I think it depends on how much coding you’re doing. If I were you, I’d probably base it off similar rates to translators where it’s determined by every few thousand words or per page.
I don’t think I’d charge if the scenes were relatively small/short and didn’t make up a decent chunk of an episode (obv I don’t know how much you’ve coded/how long your scenes are etc).
But that’s just my opinion without knowing the details. 