If I read that right, the mark at 5' is the center line of the car, left to right. Not sure why you need it started so high.
Then measure the distance from the ground to center line of headlight and use that for up and down adjustment.
Then measure the distance from the center line of the car to the center line of each headlight and put that on the wall. You are going to end up with a line down the wall at center line of the car (vertically) and a line at headlight level(horizontal) with two lines showing the center of each headlight. (or 4 if you do the low and highs)
The instructions don't include how to properly aim the headlights though.....