10-12 is a cb-radio 10 code which means "visitors present". It was a way to let someone on the other end know to be careful on what they said. Today it can be used to warn someone to stop talking about something or to be careful what they talk about at that moment.
Hey we got 12's.
Uhmm I was going to say something but there are 12's.
At one time 10-602 was a CB code for wanting to have sexual intercourse with someone. "602" was abreviated to mean I want you (sexually).
Hey Baby 602 right now, right here.