Thread:ADour/@comment-3965848-20181020090942/@comment-4651179-20181028231501

TRN numbers are not chosen arbitarily and must always follow the sequential order. If you want Earth-TRN700 instead, you'd have to wait until somebody creates Earth-TRN699 first.

Usually you can find here when new realities are assigned official numbers. There are usually users like MarvelBoy2002 keeping track of updates in the appendix to let us know of new designations.