"take a number"

As in, "I would love to meet that sweet girl" ....

"Sure...take a number !"

It means "Wait your turn" . Many bakery's have more customers waiting for service than help behind the counter. I'm sure you've seen small red plastic round-like boxes that dispense numbers for people to take and wait until "Their number is up" (another phrase from this situation). I remember when they first installed this contraption at the Department of Motor Vehicles. I went toward the counter for help and was told "Take a number, please and we'll call it when it's up". (Ok I lied they didn't say please.)