I believe it is the same on the 737, but i have to check tomorrow. If i remember correctly it is based on GW, CG% and flap setting.
And of course in boeing speak a derate means a fixed derate with a complete new set of performance data (VMCg/a for example). Derates on our 738s are 24 and 22k, 20 and 18k on our 700s. Base thrust setting is 26k and 22k.