Waters GCT Premier Operator's Manual page 64

Instrument Setup Wizard Detector Setup:
The wizard automatically calculates the detector setting that is required
to detect more than 90% of all the ions produced.
During the procedure the detector voltage is set so that the intensity of
the signal no longer increases as the detector voltage is increased. To
ensure optimum sensitivity and mass accuracy, check this value
periodically.
Setting the optimum gain for the detector on page 10-52.
See also:
When completed, the Instrument Setup Wizard DDTC Setup window
appears.
3-12 Tuning the Instrument