I have used the Pressure Trace on just one cartridge and rifle so far -- the 6.5 Grendel in a TC Encore.
The first thing I discovered is that the lug under the chamber significantly reduces the strain seen even at the top of the chamber where my gage is located.
I therefore tested close to ten loads from two different powder manufacturers to calibrate. Now when the system says "50 ksi" I know that it means my load has a good chance of being within about 5% of that pressure when tested in the powder manufacturers' pressure breeches.
It dies NOT mean that actual pressure is 50ksi, only that the number has a good chance of being consistent with published data.
BOTTOM LINE: When possible, test against known loads before assessing your own loads. If you have a wildcat, try at least to pressure test with known loads in the parent case.