"50 years ago..." COS timing question - COS spoiler

[lipscombgene]

COS says that Hagrid was expelled 50 years ago and that Dumbledore 
kept him on as gamekeeper after that. That would of course make 
Hagrid something like 60+ years old.

In GOF, Molly Weasly remembers being a student at Hogwarts and talks 
about her memories of the gamekeeper BEFORE Hagrid who was there when 
she was at school.

How old is Molly?

It does read this way, doesn't it? Or have I missed something?