I find 3.5/ is the Easiest
Whether you’re using the the coordinate box or the tracker, there are a lot of ways to write a number. Some are easier than others. A quick rule of thumb is that ArchiCAD recognizes fractions as inches, whole numbers and decimals as feet. So… a couple of ways to input three and a half inches: .2916667′ .2916667 0-3.5″ 0-3.5 3.5″ 3 1/2″ 3 1/2 3.5/1 3.5/ 7/2″ 7/2