go read Dan Lilja's article on determining what your clicks really are. Very few 1/4 click scopes are actually a correct 1/4.
Basically measure off 30" at 100 yards 2 dots and lock gun down with bags and see how many clicks it takes to really move from one dot to the other. that will allow you to determine the actual value of your clicks. They can be off as much as .010-.020 of an inch, ie ie instead of being an actual .250 they could be .240 or .265.
I might also add that you might want to learn and setup your chart in Minutes of Angle instead of clicks. Most programs will readout both. If you needed a hold over at 600 yards of 73.5 inches or 49 clicks you would have to count 49 clicks, nearly a full turn on your scope. If you set your chart up in MOA you would need 12.25 MOA. Simply turn the elevation turret to 12 + 1 click. The MOA system is much faster and less likely to make a mistake on. No matter what you use you will need to shoot at the range you intend to use the system at to confirm your chart prior to use in the field. You may find problems like Bounty Hunter spoke about where the click values are not exactly 1/4 MOA. I had a Leupold LRT 6.5-20x that had .25 windage but the elevation was .34 MOA. I discovered this when confirming my drop chart. By the way Leupold quickly fixed the problem for me.