"It's perfectly okay if you don't understand every single one of them. For one thing, I make a lot of corny jokes, and you have to be 40 years old to get some of them"

This quote by Brian P. Cleary is a reminder that it is completely all right to not comprehend whatever. He is saying that he makes a lot of corny jokes, and some of them might be too old for the listener to understand. This is a suggestion that not everybody will comprehend whatever, which is fine. It is likewise a suggestion to be conscious of the age of the audience when making jokes. It is important to be aware of the age variety of the people you are speaking to, and to adjust the jokes accordingly. This quote is a suggestion to be conscious of the age of the audience and to not be prevented if not everybody comprehends the jokes.