There's a flaw in calculating approach shots

There is an inherent problem with all the watches on your second shot to the green. Take this scenario:

You are on a 400-yard hole, the tee is at the back of the green, about 30 yards from the center. Your drive is 250. When you take your second shot, I assume the watch knows at that time the drive went 250. You nail your second shot and you come within inches of the flag. The Center of the green was 150, the flag was at 180.

Now here is the problem. Does the watch record 150 as your shot or 180?

Hummm?