See the below article for information on calibrating and/or adjusting the sensors on the 2456 Piston Gauge Monitor. The documents and procedures are the same as for the 2465 Autofloat Controller (legacy product - no longer available) that has some additional features/parameters (barometer, control coefficients, control sensor) that the PG Monitor does not have.
2465A Autofloat controller, How to Calibrate its Sensors
and this article,
2456 PG Monitor and 2465 Autofloat Controller - Calibration and Status Window Information
For questions contact Fluke Calibration Pressure Technical Support at the below link or by calling 1.877.355.3225