Don't get too wrapped up in this figure. It doesn't make a lot of difference. I just went to http://www.vortexoptics.com/content/lrbc and entered the following info:
Factory Ammo - Black Hills Gold .308 Win 168gr AMax 100 yard zero 4550ft elevation 45 degrees, 58% humidity, 25.47" pressure
Try it for yourself. I leave the scope height at the 1.75" default anymore. Worry about reading the wind and not scope height in tenths of inches. One less thing to worry about.