They have to build the lines with a min of 10 days off. However most b/u and hard lines seem to have at least 11. If you're on reserve, they'll try to give you only 10 days a month, but if you know how to "work" the lines you bid, you can get yourself an extra day. I've had 11 days off a month since I started, and I've been on reserve the whole time. This month I have a b/u with 11 days. I haven't been junior manned while on reserve (knock on wood), but we'll see what happens now that I've got a b/u.

If they assign you additional flying at the end of the last day of your trip for a repo or just more flying, it's an extension. Extension pay is 2.5 hours over guarantee, or what you flew, whichever is greater. It only counts as a junior man if they extend you for more than 4 hours. Getting called out of the hotel early on the 2nd day of a 3 day doesn't qualify as an extension or jr. man.