If your line of sight with the scope isangled downward (shim in the back) relative to the bore then the POI will be high at any distance beyond a few yards. The bulletis crossingthe line of sight a short distance in front of your barrel. Keep shimming the back of the scope up and the angle continues to widen and you while shoot even higher relative to line of sight

Shimming the front of the scope brings the bore down relative to line of sight.

Draw it on some paper and it should become clear to you.