Ah, I see - thank you for the context! If you don't mind one more question - do you have to leave a substantial amount of cash in the Steam account in case of very late refunds? Or does Steam just send you an invoice or something?
As for refunds AFAIK if you have bunch of refunds later they will just be substracted from future sales. But games I worked on didnt have refund spikes so no clue how Valve handle situations with mass refunds.