Luda’s answer to “How can it be the original timeline the one in which Barry has brunch with Julia if that was the da…” > Likes and Comments

I guess it confused me because the setting of both scenes (the November 4th at the beginning and the one at the end) is practically the same.
So at the end Barry returns to a memory of a November 4th that we never read about?

How does Barry know which of his memories are from the timeline where Slade kills Helena and which are from the one where Ann gets FMS (so it must be the at least second timeline)?