Dorothy, OBC is on board credit.
I guess since we've already bought carnival funship dollars AND had them sent to us, it won't make any difference whether or not we continue doing that vs putting them on our account. We'll still have to visit the dreaded pursers desk anyway to unload the dollars that we have already received.
Oh well - live and learn. You don't even have the option for the other cruise that we're going on later next year (Princess). You can't buy squat ahead of time.