Yep, trouble with a type.
The website for the stevia glycerite mfr. was the first place I checked. Zero useful info: "Add 3-5 drops to a cup of tea or coffee. For use as a nutritional supplement." Not exactly helpful. 3-5 is an awfully big range, even assuming I could translate that to, say, a teaspoon's worth of sweetness, which I would certainly not count on.
"Time and trouble will tame an advanced young woman, but an advanced old woman is uncontrollable by any earthly force." --Dorothy L. Sayers