taken from the zero wing dialect (see all your base are belong to us). stands for you know what you are doing, or we're counting on you. Usually achieved by launching all zigfor great justice, when we have no chance to survive and are making our time.
One uses this phrase to point out that the listener is or the listeners are capable of finishing some task.
Alexander: I'm going to call the guy, and convince him that we are right about this.
9001: You know what you doing!
Alexander: Thanks for the encouragement.