Only the final rank of the game count.
You have the usual elo system: more your opponent have elo, and more you will gain elo if you win, and less you will lose elo if you lose.
And you have a k-factor which multiply your points win or loss if you are in your first few games.
And on this game:
https://boardgamearena.com/table?table=325886515
You finished second with another player (same points, same tiebreaker).
All k-factor were 20, except the winner which is new to the game, and got a k-factor of 40, his points gained or losed was doubled. He win and gain about +25 against each opponent (+13 * 2).
About yourself, you lose against cvn, and lost 15 elo. You win against pottle and win 8 elo (way less because his elo was way higher: 0 vs 100). And you tied against another player with 100 elo. Since you was expected to win more than him on average you lost 2 elo against him (which is few).
(-15) + (8) + (-2) = -9
And you get -6 elo this game which is very weird. I have no idea why there is a big difference between -6 and -9 that look like a bug? At least on the display.
But I hope you get the idea though.
