Afraid Number

Listen here, you chucklehead, let's break this down. You see, you're the type of person who probably thinks 2 + 2 = fish. This is a wordplay joke. The number 10 is in the middle of '9/11' and that is a scary thing to be in the middle of, since 9/11 was a very scary event. The joke plays on the juxtaposition of harmless number and a tragic event.