Normally, if you are called on your last reserve day for anything that spills over into days off, that would be junior man pay, normally with compensatory days off later in the month.

If your schedule originally had more days off than the contractual mins, I suppose they could make you work on your day off without giving you another day off as long as you didn't go below the min. But I think most reserve schedules take you down to min days off anyway.

If you have no contract or policy on min days off, then you can theoretically work straight FAR's...meaning you need a 24 hour break every seven calender days. This could be noon-noon, meaning you never actually get a day off.