I have always wondered if the actual distance is different from 20 ft up in the stand to the ground when you are ranging the same object from the same tree? Hope this question isn't too confusing, it is kind of hard to word it the way I mean it. Basically, if a deer is 30 yards from the base of the tree, would it read 30 yds. on the rangefinder if you ranged it from 20 ft. up in the stand?

Your range finder would read the the straight line range (distance from you to deer). Although you only need to worry about the horizontal range (distance from tree to deer). Gravity ,for hunting purposes, only affects on horizontal range. changes in elevation don't make enough of a difference to affect arrow flight. To use your rangefinder simply sight a tree at eye level close to the Deer, that will give you the correct bow ranging.

kelincp is right on the money with his answer.