GS on reserve math. If you fly a GS all on x days, you get 9 hours free from duty THEN you get 24 hours off for each x day interrupted. So, if you end your trip after 1500, let's say 1700, you get 9 hours free. That puts you at 0200 then 24 hours off for each x day until 0200. So on your next LC days, your LC obligation would start at 0200. It would show up as (let's call it a 2 day GS) two PB days and a PR day (from 0000-0200). If you have no more LC days, and since the program can't do partial payback days they would deposit 3 PB days in your bank. Otherwise, they'd be getting a discount if you fly a GS on x days after fulfilling your LC obligation for the month..