MSD inclined manometer measurements?

[Machined]

I got the article off a site but I can't definitely make out the measurements for the inclined manometer. Does anyone know the exact measurements? It looks like the scale is 29 inches long with a 13 inch vertical drop. Is this correct?Also in making the scale do I simply square each percentage and then times it by 29 if that is in fact the length to get the length on the scale that each percentage point is to be marked? Thanks alot