I think it's like pressure gauges, especially for a non professional. It's not as important what pressure you run, your butt will soon tell you if it's too soft or to hard, it's about being consistent. If my tyre gauge says 40psi and it feels good, I pump the tyres to 40 all the time. Do I know that it's actually 40? Of course I don't. I checked it a few times when it was new and it returned similar readings to my analogue gauges, but beyond that it's not really worth making sure it's dead accurate just that the tyre ends up the same each time I use it.
Use the same pressure gauge on all tyres all the time, use the same spoke tension meter on the spokes all the time and it's the consistency more than the accuracy that matters.
....and good luck!