A customer is drinking beer in a hotel. What does this article mean after he drinks the second cup?

This is actually a joke. When customers were drinking, they found that the hotel owner gave them only half a glass of wine, so they told them how to get the boss to sell 70 barrels of wine every week, as long as each glass was full. It turns out that half a cup can sell 35 barrels, and full can of course sell 70 barrels.

But from this joke, we can see that we must be conscientious, honest and trustworthy, and give our customers the greatest benefit in order to win more customers.