Pathfinder 1E beginner box with "new book inside"?

[Ezequielramone]

hey, i have ordered the beginner box and just realized it have a text in one corner that says "new book inside".
Does somebody know what is that new book?
I can't find it.

 

[fjw70]

I think the new book is a transition guide from the BB to the ful PF game.