Did you just finish training? HR told our class that a lot of people were calling them because they didn't understand how it was set up when you leave training. They explained it to us so they could avoid tons of calls. Let's say you finished training in February:

November: You get paid training + training per diem
December: You get paid training + training per diem
January: You get paid training + training per diem
February: You get paid training + training per diem
March: You get paid guarantee (NO per diem)
April: You get paid guarantee + March's per diem + March's overtime
May: You get paid guarantee + April's per diem + April's overtime

There is a month lag for per diem and above guarantee once you actually start flying.

If you aren't just finishing training, then this doesn't apply, obviously.
Good luck!