The truth is that, I do not really know how a rack is scored. I know that in one system, inches are lost for some reasons. I can't make sense of that. If it is there it has to count.
I am now curious however. Maybe I will find out how to do it just to measure the 3 on the walls. I live in PA and they are more than "spikes and forkhorns". I know that they are special to me and that is what is important.
If I ever get around to it, I'll publish the results.