Just ran into this again today leaving HHN:
B744, GE CF6-80, OAT 10C, Assumed Temp 54C. Selected CLB thrust in the FMS (usually use CLB1) due to altitude restriction. At 1500' N1 INCREASED 4% when CLB was activated.
I've run into it before. It just shows that with Assumed Temp thrust settings, CLB thrust is based on full thrust, not the Assumed Temp thrust.