A surprising topic.
If you think the tacho is over reading by 300 to 500 rpm then you should never have left the runway. Given the average spamcan's static rpm it would have been on the redline early in the takeoff run.
Even more importantly if it had been under reading, the engine could have been severely down on power. This is the last chance you have to check the aircraft is going to perform the way it is supposed to and clear the far hedge, fence, wall, hill.
Obviously if you are chasing rpm settings you do not have much experience - but do read the flight manuals and KNOW the expected static rpm from the aircraft at full throttle - if you do not get that do not fly. It can save more than just embarassment!