Keysight Technologies N4000A SNS Series Operating And Service Manual page 73

Caring for Connectors A
Apply only enough pressure to the gage so that the gage pointer settles at a
reading.
Gently rock the connector gage within the connector, to make sure that the gage
and the outer conductor have come together flatly. Read the recession (or
protrusion) from the gage dial. (For maximum accuracy, measure the connector
several times and take an average of the readings.)
Rotate the gage relative to the connector between each measurement. To monitor
connector wear, record the readings for each connector over time.
Keysight N4000/1/2A Operating and Service Manual 73