300

Definition of “being 300” is being 16. The jokes comes from a interview chief keef had where one of the interviewer said chief keef was only 16 and he replied saying no he wasn’t and the interviewer said then how old are you and he proceeded to tell her he was 300 because he didn’t want the world knowing he was 16

Girl: he’s only 16
Guy: no I’m not
Girl: then how old are you
Guy: I’m 300