A farmer had to count his sheep for taxation purposes, so he got his border collie to do it. The dog came back and announced that there were 400.
The farmer thought that maybe he shouldn't take a dog's word for it, and very carefully counted them himself. There were 397.
He scolded the dog "I gave you a very important task and you said there were 400 sheep. I've counted them, and there are only 397"
"I know" said the border collie "I rounded them up"