Score is your MMR, adjusted by Prediction vs Outcome, and reduced if you have not played much.
Prediction vs Outcome: Wins and losses always count, but expected results move the score only a little. Strong wins help more, and bad losses hurt more.
The low-game penalty eases off as sample grows, and it is lighter now once a player has a solid number of games.
Games under 120 seconds are ignored.
Score = MMR | PVO | ACTIVITY, All 3 count towards score.