Ranger Mods

Hi, I have installed 4 TPMS12 DE8T-1A180-AA pressure sensors on my set of off road wheels/tyres (other set for normal town use) which work well with the Ford display and my scan gauge which I have set for monitoring each wheel. However I notice the scan gauge indication for all 4 wheels seems to be 3PSI lower than my manual gauge (I have 3, one digital and 2 analogue).
Has anyone else noticed this?

My actual tyre pressures and OBDLink readings are under one pound in variation

Mine are pretty much identical to my digital ARB gauge.

Are the pressures linear? Drop to 30 compare, 35 compare, 40 compare. If linear then try MTH 0001 0002 0003 which will add 3 PSI to the reading.