When you ask a girl for her number and she writes something down and walks away. It's not until after she's gone you realize she gave you 6 numbers instead of 7 (not including area code).
Adam: Yo Paul, I was clubbin last night and then i saw this hot girl and asked for her number. I only got 6 digits, Look at this!
Paul: Dude you got fuckin 6-digited. She totally isn't into you.