The calc is used in true airspeed for the turn radius and bank angle calcs, which is the arithmetical way of extrapolating out the ground distance (which the design programs use) vs the air distance at altitude with respect to the curvature of the earth....
(see the crap we have to deal with)
sorry, to answer your question, you are correct, its written poorly, its in feet, so 1500 isnt 1.5, its 1500, as it seems to state)
also, there are several significant addendum to this root document...so this doc is not entirely accurate. (good catch)