When the plans or instructions give a throw measurement, most give the added information about where to measure it. And almost always it's the widest part.

BTW, don't get too intent on getting the throw exact. Close will do. Their amounts are chosen to be safe for their CG location which is usually also a very safe one.

You and the airplane will sort out what the CG really should be as well as the throws from flying.

They don't usually tell you where to connect the pushrods to the servo arm and horns. That's actually worth mentioning. It's often just luck of the draw for a lot of beginners. The one thing you want to be sure of, is to have the connection at the servo shorter than the connection at the horn. That insures the servo will have good leverage to begin with and you'll have a good start with those connection adjustments. Lots of builders simply hook the pushrod into the servo arm at the inner hole and then see if any of the holes in the horn work to give the throw needed. That insures the levers at each end are favorable to the servo. But there is a 2nd step to that that does even more.

If the connection at the horn doesn't wind up in the outermost hole, it's worth doing a second round of adjustment. If there is an open hole farther out the horn, and one farther out the servo arm, then move both connections out one hole. Try the throw and if it works......... you've kept the leverage in favor of the servo. Always a good thing. And you've reduced the play in the system's ability to affect flutter.