On Denon receivers both, absolute scale and relative scale, have 100 divisions. So, one can make a gross equivalency that, Master Volume change of 1 unit on the absolute scale equals 1dBSPL. A logic leap, that the scales are equivalent other than manner of numbering (0 to 99 vs. -80 to 18), is valid only in this scenario.
Had the absolute scale been 0 to 25, a volume change of 1 unit would be 4dB.
Had the absolute scale been -50 to 0, a volume change of 1 unit it would be 2dB.
Had the absolute scale been -603 to 1111, a volume change of 1 unit it would be 0.06dB.
On the absolute scale, volume readouts pertain to that system only and sensible in making relative assessments intrinsic to that system. Speakers are highly different in efficiency and get placed at varying distance from listener. Therefore, 75 dBSPL will be a different absolute scale number on different systems. Indeed, even for the same system in different rooms. Making a generalization that, "on most systems absolute volume of 80-82 is reference level" shows a lack of understanding the fundamentals.