Clarification on the measurement of the speed of a motor

Hi,

I am not familiar with the Meccanism module, so I ask for your patience.
I applied a motor to a rotating body by defining the trend in a table:

Still from the engine definition tab, I see its graph and so far everything is ok.

My problem appears when I ask the program to detect the measurement of the motor speed in a kinematic analysis, I get this result. I would have expected to obtain a graph similar to that of the engine and instead they are different, why?

Thank you.
P.S. I'm using creo 9.0.0.0