That's what's called a trim level for adjusting a particular speaker or pair of speakers generally, and the range can be +/- 10,12, even 15 dB, just depends on the brand/gear involved. A dB reading on an spl meter for 75 or 80 would depend on a few things, but generally the test tones you would measure at those levels is for calibrating the system overall, to level match among the speakers/subs and to approximate a known standard like a THX movie level...nothing to do with individual trim levels particularly except to adjust a particular speaker/pair of speakers to match others in the system (or to raise/lower it to preference rather than reference). What are you trying to do particularly?