Most often when you calibrate an instrument, there is a tolerance limit (acceptance limit) set in advance for the calibration. This is the maximum permitted error for the calibration. If the error (the difference between DUT and reference) at any calibrated point is larger than the tolerance limit, the calibration will be considered as “failed.”
In the case of a failed calibration, you should take corrective actions to make the calibration pass.  Typically, you will adjust the DUT until it is accurate enough.