With a 6:00 hold, that would depend on the size of your aiming bull - which dictates how far the center is from the POA. A group in the center of a 10" bull isn't the same distance from POA as one centered in a 20" bull.

What you have to do first is find your POI with a specified distance, POA, and bull size. Then you can calculate sight height to zero at another distance and/or bull while employing the same perceived sight picture.