That means it's in reference to things that were considered officially created for Version 1 Twilight. So the V1 rulebooks and adventures, mostly.
Some things were changed for V2 to reflect the change in time span that occurred between V1 and V2. Thus, you ended up with some differences that conflicted with V1. So you then have a V1 timeline and a V2 timeline. Thus a V1 'canon' and a V2 'canon'.
And, as a personal pet peeve of mine....the word 'canon' is used incorrectly in the context that so many use it. The material is official, not canon. But it was something that someone...who knows who and who knows when, used incorrectly and people have just run with it since then. It just rubs my fur the wrong way. Nothing you did though.
