Originally Posted by iaflyer

I don't think it's contractual. Well - not directly. I think it comes from the fact that any report time on SC has to be in your SC window.

So - say you go off short call at 11am. Since the call out is about two hours, anytime after 9am the report time for a trip should would be after 11am. So - there isn't any use for you after 9am. Therefore - scheduling would release you after 9am because they effectively couldn't use you. (They can't assign a report of say, 11:15 because then you aren't on SC anymore).