Or another, simpler way to put it is:
C.R.C. + ABIEGNIS = VITRIOL
(You got your subtraction backwards.)
@Galahad said
"Also, where does Abiegnus originate? I don't recall it from the Fama."
Other Rosicrucian documents.
"And why does the C.O.T. article describe 72 as "[p]robably the most important theoretical no. in all of medieval magick"?"
Lotsa reasons - my notebook page on 72 is more like 2 pages. But most of the reasons boil down to the 72 pentades of the zodiac and their attribution to things like the Shem ha-M'phorash, the Goetic catelogue, etc. There are other important clues in the Latin Qabalah Simplex catalogue you consulted.