It has been a while since I posted last (like, a decade?)

Anyway I was reviewing The Spinward Marches Campaign and on pages 12 and 13 there's maps of the progress of the Fifth Frontier War with labelled areas but... there's no key to the labels.

The numbers are Zhodani an Imperial fleet numbers? 

D, N, J, G, S, C, U are...

D - Darrians

S - Sword Worlds

G & U are Vargr forces since they're coming for Coreward

N, J, C - ?

Anyone ever decipher this? I don't see a reference in the book itself.

Thanks!