I imagine that, since you're allowed to schedule a new FP each time you use one of your 4+ ones, then if you ride at the beginning of the window and head straight to a kiosk, you can get another one for whatever is available at whatever times are offered ... So if the PP FP is 7:25 to 8:25, but you ride at 7:25 and are off at 7:35 and go to a kiosk and find a FP available for BTMRR for 7:50 - 8:50, You'd be allowed to book it. It overlaps with PP, but PP is no longer an active FP because you used it. But you can't sit down and schedule them that way up
front.