Hello,
First, make sure that your encoders are 5-Volt Differential Quadrature encoders.
To find out the correct counts per rev, check the label on your encoders, or the specs on it's product webpage. Usually, on the label, they'll print something like 2.5k counts which means that you get 10k counts as it is a quadrature encoder.
If you're still unsure, you could always wire the encoder to the motion controller and rotate the rotor of your motor by one revolution to see how many counts it's sending to Mach.
NOTE: you can check the current encoder counts (or absolute position) from the DSPMC or HiCON Status window. You can find out how to access the status window from the Mach3 or Mach4 Software integration manual.
-Marc Lim
Vital System Inc.