I didn't know as well but @JReadsAndShiz answered it for and this is what they said
It means that it does not affect the main story or is it a part of it in any way apart from the fact that it is indeed an "alternate universe" of the main story where something happens differently, in short this does not effect the future of Ennead and is merely fanservice.
what you are saying is spinn-off
it means its about the main universe not fanservice
oh really, what I though it meant was that it's basically has nothing to do with the main story.
Omaigaddd thank you so muccchhhh to take your time to explain to me ( i use to 3 times bcoz my English is so limited ) i love you and stay safee
Thank you so so muchhh for this explains i accept both of the idea because i want to learn more and more english. Hehehe although reading yaoi is not the best way to learn english
it doesn't matter and i am not good at english ... i'm turkish but i'm trying to learn english and spanish i hope you can learn english with reading yaoi
(≧∀≦)
Im SORRY gais if this is out of topic BUT
What is canon