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If the ELO ratings system is used for game play, then i think the difference in points (22-23 points per match difference past 20 games) is divided by 2 for the lower rated but the differing amount if by one point (23/2=11.5 givning 11 and 12 to players with higher number to higher player) or some type of variant as well.

All I know is that if I defeat an opponent 300+ points higher, I get +11 in ratings points and -1 or -2 if in loss but +11 if win against +100 points higher and say -5 to -6 if loss, so not sure how the whole thing is calculated.

I think the system is some type of system based on the ELO ratings system. Perhaps looking this up in wiki or searching the forums with the Keywords "Rating System" might help as well.

Chess.com uses the Glicko system. For more information check out this article: http://www.chess.com/article/view/chess-ratings---how-they-work