tailor's tape should be in inches shouldn't it? idk...
here's what I posted on your other thread:
I'm assuming those numbers are the holes. Here's what you do, grab a measuring tape, figure out the distance between the center of the two discs. That's your stance length.
Also, when I set-up my friends boards, I measure their shoulder width (to make it square with your body/base of support) and shin length (to make it square with your knees) and either average it, or use somewhere in between those two.
Another tip is jumping up on a flat surface as high as you can bending your knees towards your chest, land flat on the ground the measure the length between the middle of your feet. That would be your comfort zone (which I think will be too narrow for most).