point system makes no sense!?!
The way it works is you win (or lose) about 10 points for beating (or losing against) someone who is rated the same as you.
You win more than 10 points if you beat someone rated higher than you.
You lose more than 10 points if you lose to someone rated lower than you.
The system is not chess.com's, is a system used by other sites, and even other games than chess. It's called the Glicko rating system (similar to Elo rating system).