Hey guys, I was just wondering how to properly adjust the dioptre adjustment on my D70 Viewfinder.

My pics aren't quite as focused as I think they are when I view them on the screen and I think the dioptre adjustment has to do with it.

Also, what is the 'normal' setting for non myopic/presbyopic or whatever opic people ? Is the 'adjustment tab' (no clue what's called) supposed to be in the middle? Or right at the bottom for example?