User blog comment:B214/Question and Answers 6/@comment-29362784-20161221212439/@comment-10330822-20161222013728

Not quite. You see, Ultimate, High, Middle, and Low are the "official" classes of demons, its how they are ranked. Even if you are a Satan or Super Devil, you are still an Ultimate-Class Devil in rank.

Satan-Class means you have skills equivalent to one of the Satans, either past or present. For example, Tiamat is a Great Dragon King, but her power is equivalent to a Satan-Class Devil. So, you see, you don't have to be a devil to be Satan-Class.

Super Devil is the same thing, it simply means your strength is beyond the normal definitions of what being a devil means, almost like you are something completely different. Sirzechs and Ajuka are so much stronger than the original Satans, its almost like they are not devils at all. Hence why the term "Super Devil" was made for them.