Prodigy 3 Brake Controller

I just installed my new Prodigy 3 brake controller. It was very straight forward and
simple, my question is i seem to have about 0.15 to 0.25 volts (bounces around) on the stop light screen. Should this be at 0.00 volts when brakes are not depressed,and no trailer connected or is there always residual voltage in this line.

Thanks for any advise on this subject in advance