Reddit reviews -1 Year war record all Mobile Suit Gundam strategy tactics Encyclopedia (Entertainment Bible series) (1991) ISBN: 4891891777 [Japanese Import]

I'm not sure what game/Manga you're speaking of but no, Another Century's Chronicle is not related to any particular other source. It's just a fairly recent publication that focuses on the OYW. The name was because ACC was a series of books which also covered Patlabor and Ghost in the Shell.

EB 39 is the rarest of the EB series and also is probably the most extensive source for information on the One year war prior to the publication of ACC, which makes some minor retcons here and there.

Gundam Officials is usually pretty reliable in terms of details (as it was intended to be definitive) but conveniently leaves out numbers for the most part, limiting its utility.

Even after all this time, none of these books wants to give the Pegasus-class a definite MS capacity, ha.