If you want to learn more the research member I talked about here then take a look at his deviantart matches (specifically the comment's section) he made here and his response he made in the comments of this match here
While I am not a Demonbane expert and am far from the most knowledgeable person about higher dimensional mechanics, I can fully explain why EGD is ranked as it is.
Nyarlathotep is capable of easily creating Klein Bottles, objects that contain infinite multiverses, infinite dimensions and infinite possiblities. Considering how Nyarlathotep exists beyond these Klein Bottles and has a shapeless existence of pure chaos, he/she/it qualifies for 1-A, which is being beyond dimensional space itself. Elder God Demonbane was capable of killing Nyarlathotep 400,000,000 times with merely a glare, which makes it High 1-A on account of being massively beyond 1-A beings.