Doug, Think of a straight line from your eye to the target. The arrow will travel above this line in an arc all the way to the target, only getting back down at the target. When the line of sight and the position of the arrow are at the same place (at the target), that is called the "point on distance" (POD). For me and the numbers I gave earlier, the POD is 55 yards. If the chart I put in below shows up (computer challenged -- often), You can see that the height of the arrow above the line of sight is at it's greatest approximately at half range. For my numbers that occurs a about 30 yards, so my gap is greatest at that range. Then as you shoot at 40 or 50 yards the gap begins to reduce until you get to POD where it is zero again.
The distance the arrow is above the line of sight in its trip to a target at point on range is exactly the amount of the visual gap required at any given range out to the POD that is needed to hit the target at that given range.
Again, If the little diagram came through, Look at the arrow line above the line of sight at any distance. Transposing that distance above the line of sight is what produces the bottom arc and is representative of the gap required at that range.
I do not know who drew this diagram (I did not, but wish to thank that person!) but it is exactly correct in what happens to the arrow and how you determine the gap required.
Since the arrow MUST fly in an arc, that is why I was/am puzzled that you seem to have found a way to use the same gap (elk picture) for your distances from 10 to 25 yards.
Again, I emphasize that if you have found a system that works reliably for you, do not get too wrapped up in the details. Just do what you do. Remember that when the centipede was asked what leg he started walking with, he could never walk again.
Arne
PS. If the diagram doesn't come through on this post, please PM me with your email address and I will email it to you. As I say this computer stuff sometimes leaves me in the dust.