A wife asks her husband,
"Could you please go shopping for me and buy one carton of milk,
And if they have avocados, get 6."
A short time later the husband comes back with 6 cartons of milk.
The wife asks him, "Why did you buy 6 cartons of milk?"
He replied, "They had avocados."
(If you're female, I'm sure you're going back to read it again! Males will get it the first time!)