Board Game Arena

I don't understand any logic behind the points given or removed on the Arena matches.
I had lost a game versus an opponent with close ELO (both between 300-320) and a difference of only 2 points. I got reduced 28 arena points.
Then I win a match against a much higher ELO opponent (me 300 versus him 420) and by good difference of around 15 points. I received 24 arena points.

ELO is irrelevant in Arena. Your points won/lost are only Arena points, which should be around 1500 (at least everyone starts at 1500), and are computed from the Arena points of the players.