What's the format for entering architectural dimensions?

For example, if I'm putting in 4'2-1/4" as a driven dimension, what would I need to enter for Onshape to recognize? It doesn't seem like it uses a standard similar to either Autocad or Inventor. The closest I've gotten (for the same dimension) is 4ft+2in+1/4in... which is a big waste of time... and makes me think I'm doing something stoopid.