First there are several companies that continue to pay military members when they are on leave, although there are limits and accrual for military leave with pay. I don't know of any in the airline industry though.

As for Republic

Pre-awarded MIL leave is. -2.5hrs per day for pay and a virtual credit for scheduling of 4 hours

Post-awarded (after bids) is -4 hrs for a day of reserve, -4 hours or the value of the day missed for line holder or reserve notified of a trip on that day.

Since we generally can't rejoin trips a post awarded mil day in a 4-day trip can result in -20 hrs in a month. So it's always good to ask to rejoin the trip but good luck...