Hi, this may or may not be the same as my Panasonic SA-HE70. Its volume also counts down from 99 to 0. Never having come across this before I emailed Panasonic customer service and got a reply back next day.
Being a mechanical engineer I know about decibels as a measurment of sound, but it turns out that decibels are widely used in electronics as well. It is simply a logrithmic scale describing a ratio for power, voltage etc.
Panasonic says in the case of my reciever it measures the decrease in resistance. The result is much finer control at lower listening levels where it doesn't take much power make a large change in sound level.
I would email Yamaha to get the official scoop.
