AEB help!

Ok, so i just got my canon 20d not too long ago. I have just noticed that the MIDDLE pointer of the AEB (Auto Exposure Bracketing) option is set at -2/3. When i turn the wheel (any wheel), two other pointers start moving away from that point. How do i change that middle pointer back to 0? It seems like I can't get it in the middle, even after taking out the batteries (including the small backup battery). Please help!