Casual Chat

[I-Love-Eyes]

A man wanted to enter an exclusive club but did not know the password that
was required. He waited by the door and listened. A club member knocked on
the door and the doorman said, "twelve." The member replied, "six " and was
let in. A second member came to the door and the doorman said, "six." The member
replied, "three" and was let in. The man thought he had heard enough and walked
up to the door. The doorman said ,"ten" and the man replied, "five." But he was
not let in.

What should have he said?