Yellow Sun & Max Angle are both correct !!
Airbus Fadec sets the calculated EPR @ 60 kt, and at that time the conditions are satisfied - the flexible takeoff N1 calculated will not be lower than the Max climb N1 at the same flight conditions (i.e. only at that point in time).
At THR reduction the inflight conditions are all totally different.....
i.e. temp, pressure, and aircraft speed.
The result is exactly as Max says, parameters including N1 often will increase, the sound you hear will be a rising engine note as thrust levers are moved to the CLB gate.
Moley.