FS Employees-How do you code a night shift in paycheck8

I'm sitting in my hotel room trying to figure this out last day of the pay period. Had 3 night shifts at the beginning of this assignment.

How would you code a night shift in Paycheck8 on your OT days? I was under the impression that you couldn't get night diff while collecting OT but paycheck8 has transaction codes 25--OT over 40 w/ Night Diff and 26--OT over 8 w/ Night Diff. What's the difference between these two?

Also with Transaction Code 21 being OT (Premium Rate), am I losing anything not coding it as 21?