N1120A
Pattern Altitude
They are probably doing this to help you, possibly because of an approach or departure path. When coming off the LAX coastal route, it is pretty common for them to give you a "resume own navigation" right as you leave, or even before you cross the line out of the LAX Bravo. The reason is that the route puts you right on the departure from VNY, so they don't want you getting too close, without either getting in the downwind or turning out of the way.