08xx is a panning effect. It has different behaviors for different systems:
You can give a value from 0 to 7F. 0 means full left, 7F means full right. You can obtain specific panning values using intermediate values, such as 5A.
Game Boy, Genesis/Mega Drive
XX = Only 0 and 1 can be used here:
0801 = left channel only
0810 = right channel only
0811 = both channels
Exactly like the Game Boy except you have volume control from 0-F for each channel (e.g. 08C7 for a volume of C in the left channel and 7 in the right).
Nintendo NES, Master System, Commodore 64
These systems don't support panning, so this effect will be ignored on them.