Pro Mouse question

[Man In Black]

On the bottom of my Pro Mouse, there is this selector ring. It has three spots, -, o,+

What the heck does this do? Increase mouse sensitivity or something? I fiddled with it and didnt notice anything change.

Thanks!

 

[puckhead193]

http://docs.info.apple.com/article.html?artnum=86464
its for the bluetooth one but its the same... i too never notice a difference.