As others have said, the reading on the dial is almost irrelevant. Every receiver is different. My Yamaha goes from -60 to 0. "Normal" volume for me is about -25 or -30, "very loud" is about -15. My ears bleed at -8.

Also the scale is not linear on many systems (mine included). For example. mine has a scale of 60. If it was linear -10 would only be 10/60ths (1/6)louder than -20. It's not. If I remember correctly from my last SL meter check it's almost 25% louder.