Two-thirds of the trading in a tennis market came after news the player had withdrawn
On Polymarket US, 523 trades worth $102,735 followed a published withdrawal report. The contract paid 33 cents; the last trade, 56 minutes after MSR’s cutoff, was at 32.
Published September 10, 2026 · Clarified September 20 · Updated October 25, 2026 · 4 min read
At 16:39:57 UTC on June 5, 2026, the tennis site Tennis Majors published a report that Matteo Arnaldi had withdrawn from his match against Flavio Cobolli, who advanced by walkover. On Polymarket US, the Arnaldi–Cobolli market kept trading for almost another hour.
MSR counted trades from a cutoff 30 seconds after that publication time. From the cutoff onward, 523 trades worth $102,735.48 changed hands, or 66.7% of all the dollars ever traded in the market. The last trade on the Arnaldi side came at 17:36:53 UTC, at 32 cents. When the market settled, that side paid 33 cents. Finding and contract record
The timing matters because of how the contract settles. Its walkover clause referred to last-traded prices, so trades placed after the news raise a question about the payout itself, not only about who traded when.
Fifty-six minutes of trading after the news
MSR confirmed the Tennis Majors publication time, 16:39:57 UTC, in the page’s raw HTML. Adding the stated 30-second buffer put the counting cutoff at 16:40:27 UTC, and the last trade came 56 minutes and 26 seconds after that cutoff. Timestamp evidence
Evidence explained
The measured post-news window lasted nearly an hour
June 5, 2026 · UTC · schematic timeline
16:39:57Verified publicationTennis Majors timestamp recovered from raw HTML.
16:40:27Research cutoffPublication plus 30 seconds.
17:30:28Last-15-trade interval beginsEvery trade in that averaging window came after the cutoff.
17:36:53Final trade56 minutes 26 seconds after the research cutoff.
The cutoff follows the verified publication timestamp and the stated buffer.
Over its lifetime, the market recorded 1,035 trades covering 456,605 contracts and $154,002.74. The 523 trades after the cutoff covered 296,197 contracts and $102,735.48. The post-cutoff trades were therefore about half of all trades but a larger share of the contracts and the dollars, which means they were larger on average. The lifetime totals include 66 trades from the previous day that MSR’s first download had missed. Trade tape and counting method
Evidence explained
Before and after the stated cutoff
Arnaldi–Cobolli lifetime tape · each measure uses the same split
Period
Trades
Contracts
Dollar volume
Before cutoff
512
160,408
$51,267.26
After cutoff
523
296,197
$102,735.48
Full history
1,035
456,605
$154,002.74
Work it through
$102,735.48 ÷ $154,002.74 × 100 = 66.71% ≈ 66.7%
Dollar volume totals the value of executed transactions.
Prices shifted after the cutoff. Before it, trades ranged from 30 to 34 cents; afterward they ranged from 32 to 36 cents, rising toward 36 cents before falling back.
The record shows trading continuing for nearly an hour after a documented news point, in a contract whose payout referred to traded prices. Which trades, if any, set the 33-cent payout is a separate question. MSR’s tests of possible formulas, described in the final section, fit the payout without identifying the method Polymarket US used.
Evidence tables, source files and corrections
Evidence, calculations and corrections
Calculation details
The Arnaldi contract was one of 34 created on June 3 with the same walkover clause. Two settled at intermediate values and both corresponded to walkovers. The files below retain both trade tapes, the contract population and venue settlement records. The Arnaldi and Cobolli payouts were 33 and 67 cents respectively.
Correction record
October 6, 2026 — wording correction. The prior narrative incorrectly said the tested volume-weighted averages did not reproduce both walkover payouts. The saved tapes and retained comparison table show that simple and volume-weighted averages of the last 14 or 15 trades reproduce both settlements after rounding. Payout prices, trade counts, volume figures and tables are unchanged. This fit does not establish the exchange’s actual method.
October 4, 2026: This article was rewritten as one current narrative. Earlier article versions and the duplicate finding text were removed from the public page; supporting tables, visuals, source destinations and correction facts remain available below.
Clarification, added 2026-09-20. Eight of 11 tested calculations round to 33 cents. The tested matching windows use trades after the reporting cutoff; this does not establish which trades Polymarket US used.
Supporting visual
UTC · report, counting cutoff and last trade are distinctMost reconstructed dollar volume came after the cutoff
16:39:57Report timestamp
16:40:27Counting cutoff
17:36:53Last trade
Before cutoff$51,267.26
After cutoff$102,735.48 · 66.7%
8 of 11 tested calculations → 33¢Last print: 32¢
The matching calculations do not establish the venue’s settlement method. Two cases are examined.
Detailed table
Every trade in the contract’s life, split at the counting anchor — reconstructed from Polymarket US’s own Time & Sales files
Window
Trades
Contracts
Dollars
Price range
Before 16:40:27 UTC
512
160,408
$51,267.26
30–34¢
From 16:40:27 UTC (56 min)
523
296,197
$102,735.48
32–36¢
Lifetime
1,035
456,605
$154,002.74
30–36¢
Detailed table
Every reading of “the final trades” we tested against the 33¢ settlement, rounded to the cent the way the venue quotes prices
Reading
Trades in window
Rounds to
Matches settlement
The literal last trade
1
32¢
no
Simple average, last 3 trades
3
32¢
no
Simple average, last 4 trades
4
33¢
yes
Simple average, last 5 trades
5
33¢
yes
Simple average, last 10 trades
10
33¢
yes
Simple average, final minute
4
33¢
yes
Simple average, final 2 minutes
5
33¢
yes
Simple average, final 5 minutes
12
33¢
yes
Simple average, final 10 minutes
16
34¢
no
Simple average, last 14 trades
14
33¢
yes
Simple average, last 15 trades
15
33¢
yes
Detailed table
The last n trades, averaged two ways, on both walkover contracts — against settlements of 33¢ and 71¢
Tell us which wallet, market, payout or profit claim you want checked. MSR accepts commissioned investigations using the evidence standards shown in this report.
