There is no 'angle. Measure it first with the bike straight up, lifting on the rear fender to completely unload the suspension. Top it out!
Then measure (perpendicular to the ground) from the axle to a point directly above the axle.
Then measure again with you on it, complete with all your gear. Some methods indicate 'standing on the pegs', some indicate 'seated'. Set it how you spend most of your time on the bike.
If 'both times standing upright' refers to the bike being upright, that is correct. It isn't ever measured 'on the stand'.
For anyone wanting to niggle with specifics...yes, I understand that a properly set bike will BE topped out when sitting on the sidestand, and a properly made measurement in that postion WILL be correct for the 'unloaded' value. Still, it's easier to make all the measurements the same (imo) for the sake of clarity in explanation.
Oh...when you're done, measure the amount of 'free sag', or the amount the back of the bike drops under its own weight...when sitting straight up. Should be 3/4 to 1&1/4" or so. Less means too light a rear spring, more means too stiff a rear spring.
Devol pullrods will raise the seat height a bit...1/4-3/8" or so. Sag needs to be set after the rods are installed.
Cheers!