[Cause]
Gun mastering before wear measurement reference value calibration has not been performed. Possible causes are:
1. Reference value calibration was executed with the worn electrode tips still installed.
2. Reference value calibration was executed again after wear measurement had been performed using new electrode tips.
[Countermeasure]
Check that new electrode tips are installed and master the gun. Alternatively, reset the wear amount. Then execute reference value calibration again.