Hi Tony,
To define the set-up in another way,
Check angles with brakes applied.
The objective is to set the leavers at 90 degrees to the line of the cable or rod. This ensures that maximum power goes into applying the brake, rather than forces being 'wasted' in other directions. (i.e. creating high efficiencies.)
(This goes for the primary leavers too, but often more difficult to satisfy.)
Pete