I've always thought it had to do a lot with context and so, is inexact.
When your wife says she wants to buy just a few pair of shoes this year she probably means twenty.
If y'all are going out for a few eggnogs this evening it is probably three or four.
A few children is two. A few beers with the guys is six.
A few minutes is gender dependent, as in 'I'll be ready to go in a few minutes'. For guys, it's two, for women, it's thirty.
'A few more cornsnakes' is as many as you can sneak into the cages before your wife catches you
