ahhh, I see what you are getting at. Same principle just at a more micro level.
Take captain cooks casino for feb 06. For slots you’ve got it listed at: 2.46% margin. So if that month had 2million bets placed on slots on that casino, and the other months on average had 500k bets placed on slots on that casino … you can see that 2.46% will have 4 times greater weight than the other months.
clear as mud?