Personally, I think way too much is made of this issue. The throw recommendations made by the manufacturer are just that... RECOMENDATIONS.

This is by no means a critical measurement. In my lifetime I have never measured my throws with anything more complicated then my eyes.

This really doesn't call for a diagram, but far be it for me to turn down a request, so here's what I would do if I were going to actually measure it.

Block up a ruler so that one of the inch lines is centered on the control surface, then deflect the surface and see what it reads.

To make my point about how little this matters consider a few things: Let's say the MFGR recommends 5/8 throw, and in one hole, you get just under and another, you get just over. Are you going to drill a new hole in the servo arm or just pick one? And how often do you get the maiden flight in and then decide you need more, or less control? So what do you do measure it again? No, you just move a clevis in or out.

The bottom line is, don't be over critical. It's not like an eighth of an inch difference is going to make you crash your plane. If it is, you are not ready to do a maiden flight on your own, and should have a more experienced flier do it anyway. And if you're an instructor who thinks 1/4" difference is going to make you crash, I suggest you hand in your Instructor Certificate right now.