you are right, all concentration is needed and always have to make slight allowance for air-loss. I've used a digital one in the past which is a bit better for this, but couldn't find the patience to deal with it's random ability to change setting from psi to Bar or Kpa etc. I nearly bought this the other day:-
I remember reading a bike magizine article on this subject some years ago & one of this type pressure gauge was rated the most accurate !
Yes, they have offered a refund no problems so can't fault the seller. Just a good job I had other gauges to check it against.
I compared it to my other 2, it was 4 PSI low. I had previously compared my others at a TD as my old tried and tested was not agreeing with the new one so I sat on the floor with several from around the pit to get an average.
My point really is just make sure to check a new one against some mates ones and then do it at reasonable intervals. Or don't, I don't mind what others do.
Just remember folks - a digital readout only makes it easier to read, not more accurate/repeatable. All that display is going to show is what the sensor and it's associated electronics (both easily complete shite) are sending it.
This was recommended to me by Rob at Pro Twins: https://www.topeak.com/global/en/products/gauges/351-smartgauge-d2