Qavion
Mutt has covered the 25% relationship, which, as he says is the maximum allowed. It can be modified to a lower figure (greater power) by the operator. As for the CLB derating, it changes to reflect the Assumed Temp applied and can be changed - without affecting the de-rated T/O power. My previous employer used to do just that, always using at least CLB1 even if the automatic de-rate went to CLB2.