If your scope is marked as "1 click =1/4 inch @ 100 yards", you have a minute of angle system turret (approximately). One MOA is actually 1.047 inches at 100 yards, but this little bit of rounding off won't hurt for the distance you are talking about. At 500 yards, one MOA is roughly 5 inches. You mentioned 68 inches of drop for that distance from your 100yard zero. Divide 68" by 5" to convert inch drop to MOA drop, then multiply by 4 (to find the number of clicks if you want to count clicks). Or if you turret has MOA markings, just dial the MOA (13.6) which you would round off to 13.5. Be sure to shoot this solution for real on the range, because that is the ONLY way to be sure it works. I don't know how much experience you have, so if you have not heard of "trajectory validation", you definitely want to check it out. Drop charts are just paper until PROVEN in the field. Have fun shooting!
The simplest approach to your question is on your drop chart. The second column shows the drop in MOA. If your turret doesn't have MOA markings, just multiply that 13.0 MOA drop by 4 and dial 52 clicks up. Where are you getting the velocity figures on that chart from, a chronograph, or from a load manual? Load manual numbers are VERY approximate (so much so as to be pretty useless for anything other than zeroing at short range) but if that is a chrono number it should be fairly close. You still must shoot the actual data to confirm, and do trajectory validation for good data in a final verified form. It will also be beneficial to run a "box" test on your scope to verify the 1/4inch per click at 100 yard specification, and take that variable out of the mix.
I meant 68"(path)/5(500yds) *4(clicks per IPHY). = 54 clicks
See the difference between 52 clicks for adjustment in MOA -vs- 54 clicks for IPHY? And you say that 14" was good (56 clicks)? Better figure out what you have for actual scope adjustment.
The term 'drop' should never be considered in solution. It holds no meaning in the field.
If your scope is in .25 inches per click then why not change shooter to IPHY? If you wish to come up 68" at 500 then shooter will do the math and give you the solution in IPHY. Assuming that for every 4 clicks you have a leading number such as 1, 2, 3, 4 you only have to count every 4th click and dial 13.5. If not, then you have to count 54 clicks etc. Just seems easier to use IPHY.