So you get the bead sight picture you want.
If the adjustable rib physically moves the front bead up or down when you adjust it, you'll this will also change your POI.
Most guns don't have adjustable ribs.
If you have both an adjustable comb and an adjustable rib, its kind of a trial and error thing.
Adjust the comb, then adjust the rib to get your "preferred" sight picture, then see where it shoots.
If it doesn't shoot where you want, repeat until it does.