Couple Three

Perhaps it's a generational or regional thing, but my parents have a weird grasp of language.

For instance, when they ask to be given a few things, say eggs or packets of sugar, I'll hear:

"Gimme a couple-a-three packs of sugar."

Now, correct me if I'm wrong here, but isn't a "couple of three" equal to six? Isn't it easier to specify the exact amount you need without leaving room for interpretation? One would think...