People often say that PRs automatically become PBs on subsequent awards, but that is not the case per the pwa. Scheduling sometimes even does it that way incorrectly.

It’s all just fancy coding for x days that start at times other than midnight. After you have had a GS, every x day in the block until you go back on call ends at other than midnight (unless you had an exact 1500 release). Subsequent GS all depend on how many 24 hour periods are interrupted or remaining in the block. Take a look at scenario 3 in the scheduling alert. A 2 day trip only interrupts one x day because the x day goes from 2000 on the 11th until 2000 on the 12th. So the pilot only gets one PB day for that interruption (the 9 hours take him to 0300, and the other 2 x days are from the scheduled x days he originally had on 13 and 14)