Yes there are those values that range from 1 to 5 and you can change them to whatever number in that range that you want but they directly coincide with the volume level you get and can adjust with the slider on the side of the phone. In other words, if I move my volume all the way up the number in the registry will be 5. If I move it down then the number will always decrease by 1.
Look
here at this thread for more help possibly.