I never pay any attention to this, drivers all report signal strength/quality in different ways. Eg 1 driver might report between -100 and 120 another might report between 5000 and 10000, Ok that might be a bit extream but you get what I mean! The way I did my setup was to tune my analog PVR-150 (or just a normal TV) to prime, then aligned my antenna to get the best possible picture
without the amp then added the masthead amp into the loop afterwards. This should get you the best possible UHF signal.
I have to say though, even though I'm in Auckland city and the DTT reception map shows I'm in the best possible zone the amp makes a really big difference, actually DVB-T isn't usable without it. I guess it's the hill behind the house!