With assumed temperature the max thrust reduction is 25%, so you basically takeoff with climb thrust already. If you have the option TO-1 or To-2 you would takeoff with 10 or 20% of T/O thrust, in addition to that you could use assumed temperature method (tables provided for that) which could make you takeoff with a total thrust reduction of more tan 25%, at thrust reduction altitude you have the option to continue with CLB 1 or CLB 2, which has almost no effect on engine life, but on fuel consumption++, if you select CLB thrust the engines would spool up to the 25% of the full T/O thrust which can be quite a push.