This is what Shawn is saying if I may:
Let's say your shooting at a target at 800 yards and your ACI says the cosine of the angle is right at 0.90 . You have a ballistic chart that you printed at home for level shooting, for horizontal shooting. Now because you're shooting on an angle, for one of the methods we do this:
800 X 0.90 = 720
yards. Now in the chart we look for 720 yards on the horizontal and tells us this...
The chart says that for the corrected horizontal distance of 720 yards you need to go up 15.9 MOAs.
Now using an angle of 26 degrees for which the cosine is 0.90 and letting the program calculate the right ajustment for those same conditions we find out that we need...
which makes for a difference of 0.5 MOA at 800 yards... boils down to your bullet impact will be 4.2 inches low; which is what Shawn was saying.
This error is just for 26 degrees, the steeper the angle and or longer the distance the error will multiply big time.
Yes, if you imput in Exbal all the info including the 0.90 for the cosine of the angle, you'll get the right info.
Now on the original Horizontal ballistic chart that you printed at home, if you check at 800 yards it calls for a correction of 18.6 MOA; we know it would be too much because we're shooting at an angle, so the other method we use would be you take the 18.6 X 0.90 = 16.7 MOAs which is much closer to what it should be; it will impact 2.5" high in this particular example. Shawn reffered to this method saying it was more accurate, and he's right! We need to remember that all this is at 26 degrees, not 40 or 60 which would make it easy to miss. Again, the most accurate method is the one in which you imput all the info into Exbal.
Hope this helps.