Soo I fought with support but didn't suceed, we've been refunded based on non-standard formula which ended up with refund being 250$ smaller than I've expected. Confirmation from their e-mail:
I've sent you 100%=530$ back, so including 250$ bounty that I won we've got $281.78 more to send.
20% = $56.36
10% = $28.18