Great question.
I asked that same one a while back and can't recall the answer I recieved.
Is it the middle of the screw to the limb bolt? close side? far side??


I also noticed a sweet spot on my mighty-mite when tweaking with it. I'd get a good 2 fps gain if the timing marks on the cam were just a little off than perfectly between the lines(when comparing to the limbs).

I will write down the answer this time.