You're talking about ELO. The individual games don't handle ELO so this is a general website bug, but it is a complicated calculation based on the rating of each member and the expected result. You can read more about i here boardgamearena.com/faq?anchor=faq_account_elo. I don't really understand ELO, but in this case I can see that satosan622 is rated higher than both you and ferraz52, so you would expect both of your ELO's to rise while Satosan622's should go down as you see here.

I'm not entirely sure why ferraz52's goes up more than yours, but I will note that their ELO started lower and they beat Satosan and they were expected to lose to you based on the lower ELO so I would expect a rise as the system will treat this as Ferraz52 beating Satosan622.

At any rate, I don't have any control over the ELO system and I will be closing this bug.