To Tune the Aries Step/Direction Drive, use the Aries Support Tool software and put the Control Loop in "Tune Position Loop" mode.
See hardware installation guide for description of tuning parameters.
Page 78, Tuning. See link below.
From the Terminal Emulator, you can send commands to look at the actual values of the commanded encoder count (TPC) vs. actual encoder count (TPE) to determine percentage of following error.