Symbols on bottom of Apple Pro Mouse

I don't think anyone's posted this before, so here goes:



On the bottom of my Apple Pro Mouse, there seems to be a small "turning dial". Well, it's not really a dial actually, but it's hard to explain (everyone has them, so they'll know). Now, what's strange is that I can set this dial to three settings. One of the settings has a minus sign on it, another has a plus sign on it, but the one it's set to right now has a circle on it, and it's between the plus and minus ones (with the plus one to the circle's right and the minus one to the circle's left). So, does anyone know what these different settings do? I'm very curious.

they adjust the amount of pressure it takes to actually click the mouse. i didn't find the 3 settings that different from eachother, though...

Yeah, they don't seem to be that different at all. They're nearly identical. Anyway, thanks for your help, dtx3000.