The MBM temp gagues

Does anyone else have the Iwill P4R533-N mobo? The reason I ask is because I can get 3 temps from it (using MBM) and I have no idea which is which. So I was hoping somebody might have figured that out already.

Also I'm not sure how hot is too hot. I've started oc-ing my box, but I get concerned that I may be heating things up too much.