User blog comment:Scorcher007/Analysis DAN up to Z2/@comment-27516045-20180828133630/@comment-35470197-20180828214936

FGH is not a hierarchy of ordinals with fundamental sequences, but a correspondence which sends ordinals to functions under a fixed system of fundamental sequences.

If you meant "ordinal with a system of fundamental sequences", then it is better to write so instead of "FGH ordinal" by the reason above, and is better to declare what system you used.