A man phones a mental hospital and asks the receptionist...
A man phones a mental hospital and asks the receptionist if there is anybody in room 27. She goes and checks, and comesback to the phone, telling him No, the room is empty. "Good," says the man. "That means I must have really escaped."

A precise location
Attorney to witness: "And where was the location of the accident?"Witness: "Approximately milepost 499."Attorney: "And where is milepost 499?"Witness: "About halfway between milepost 498 and milepost 500."