Oops -- it's taking input for an Attribute value literally, rather than evaluating the Lisp expression. Try starting with this:
and then end with
I'm not sure why it should take a Lisp expression literally but not a Diesel expression, when TEXTEVAL is 0, but as I said, I'm not very experienced with Diesel. However, if the above doesn't work, someone who is more familiar with it should be able to do the same calculation [dividing your original expression by 144] in Diesel language.