Chalis Chaurasi literally means Forty Eighty-Four (Chaalis=Forty, Chaurasi=Eighty Four). As it seemed, and later was confirmed, 4084 here is the number plate of a vehicle.
The movie, Chalis Chaurasi has Naseeruddin Shah and Atul Kulkarni in mail roles while Naseer will reportedly do an item number in the movie too.