They tied at 115 and agreed to a race to 40 so the race was extended. It is based on the final score of the match. I have never seen in football where team a is +3 and are tied at end of regulation where the person who got +3 wins the bet. As a result I do not agree with Chang wins when he won the 112th game but I certainly can see an argument over this.
To elaborate on post 496, the difference is that a football game has multiple possible ending points depending on the score, and both betting parties know that in advance. It ends at the end of the fourth quarter if one team is ahead, ends with the first score during overtime if it goes to overtime, etc. With pool there is not multiple ending points for a match. It ends at the number of games won that was agreed on, period.
For anybody who was betting on who would get to 120 first with no game spots involved, or if a 4 or less game spot was involved, either party should have the option to call off the bet once the match length was changed to a different length. Maybe they like a guy's endurance over 3 days, but not over 4 days. Maybe they only want to sweat bet a match they can watch at the same time to add excitement and give a reason to watch and get into it, and they could watch the three days the match was scheduled for but can't watch that 4th day. Maybe they like getting 4 games on the wire when it is a race to 120, but would have wanted more than that if it were a race to 155. Could be lots and lots of valid reasons why you would bet on a 3 day race to 120, but want to bet differently or not at all on a 4 day race to 155.
And in case somebody might say that for bets with no or four or less game spots then the bet should still pay off based on who hits 120 first even though they are playing past that... Doesn't sound reasonable because the players might play differently going from 115 to 120 in a race to 120 than they would play going from 115-120 during a race to 155. In a race to 120 their only goal is going to be to bear down their hardest and win 5 more games before the other guy does. But once it is extended to 155, chances are from 115-120 they are playing differently and pacing themselves more, not so worried about every game at that point, maybe even using that time period to try to free wheel and get loose and get in stroke or whatever the case rather than focusing solely on trying to win those particular games. The bet was for a match to 120, and if there is no longer a match to 120, there is no longer a bet.
Things are different for anybody that was giving up 5 or more games on the wire. That bet is over and you lost, time to pay up. That bet was lost before the the decision to extend the match was even made, and is completely unaffected by the fact that it is going to end up being extended. The bet was lost while the match was still under the conditions you expected them to be when the bet was made.