A few golden rules learned after zeroing zillions of rifles over zillions of years
Foresight INTO the error, backsight OUT of the error.
ALWAYS treat the graticle post as a FORESIGHT and
Remember the initials C=D+R. CLOCKwise = DOWN and RIGHT. In other words, turning the drums clockwise will move the grat post (which is in effect a foresight) down and right