I think I wasn't clear enough. Here is how you play a game of tenchess. (1) Play ten games of chess. (2) You get 0 points if you won fewer chess games than your

I think I wasn't clear enough. Here is how you play a game of tenchess. (1) Play ten games of chess. (2) You get 0 points if you won fewer chess games than your opponent, 1 point if you won more, 1/2 a point if you won the same number. In particular, you don't get the total number of points you'd have got by playing the chess games individually. You get 0, 1/2, or 1. In particularly particular, A doesn't get any fewer points from a marginal win than from a blowout. (Just as, when playing chess, you don't get fewer points from taking 100 moves to grind out a tiny positional advantage than from a 20-move brilliancy.) So A and B don't get 20/3 and 10/3 points on average from a game of tenchess; that's the number of "chess points" they get on average, but the average of the number of chess points isn't a thing that actually matters when they're playing tenchess. (If A wins 2/3 of the time at chess and they never draw, then it turns out that A gets about 0.855 points per tenchess game.)