The only way to tell is with a separate pressure gauge. The issue with that is the pump gauge may not be accurate.
You could use the pump on a car tire and then compare the pump reading with the pressure gauge. There is so much volume that a small amount probably won’t impact the reading. It will also indicate if your floor pump gauge is off.
I have an inexpensive floor pump that is off by 3psi. Not a big deal at 75psi, but more so at 30psi.
John