This explains how to compensate, which was not the issue.
The issue is what are the physics which account for the counter-intuitive result — point of impact is higher (and effectively equal for the same up/down angle).
Flight time doesn’t change. Distance to target doesn’t change. Drop doesn’t change (the effect of gravity is still the same).
Explaining this is where shooters come up with the amusing and the absurd.
When shooting on level ground, bullet describes an arc, gradual in the beginning, and steeper at the other end.
The measured amount of distance between line of sight and line of barrel is the bullet drop at that distance.
The bullet will always drop at the same rate, as a function of gravity.
Now,Imagine a laser attached to the scope and another alongside the barrel, the two dots are spaced vertically on the target, getting farther apart with distance.
The vertical line from the top dot (barrel) and bottom (line of sight) is the actual measured drop at that distance. This forms a long right triangle, with the 90 degree formed by the vertical small line and the line of sight.
Now, imagine a 45 degree shot, up or down, and also imagine the same triangle composed of the barrel line, line of sight, and the vertical measured bullet drop. However, even though the two longer lines, the barrel line and line of sight are still the same divergent angle regards to each other, the short third line, the vertical line, must stay vertical (the actual bullet drop at that distance)and by doing so, it's bottom will no longer touch the line of sight line because the angle between the barrel line and vertical line has changed, because the vertical line must stay vertical, as a measurement of bullet drop due to gravity, and is therefore shorter and does not meet the lower line of sight line at that distance.
If you grab a couple of long sticks and place them in a small divergent angle, and make a third small stick to just touch and close the open end, then move the first swo stickc up or down, keeping the same angle relationship between the two, while keeping the third stick still straight up and down, and it's top touching the top stick, it's bottom no longer reaches the bottom line.
Hope this helps.
:-)