F2b question

[Amber and the doods]

I'm still trying to wrap my head around this whole multi-generational thing and I'm baffled by the F2b doodles.  If an F1b results from an F1 x poodle, then wouldn't a true F2b be the result of an F1 x F1 = F2, and then the F2 x poodle=F2b? 

[M Kol]

As I understand it:

Poodle x Golden Retriever = F1 (50% GR :50% P)

F1 X Poodle = F1B

F1 x F1B= F2B

B = back-cross to poodle with an effect generally resulting on the coat and size