More Bradenisms

So Braden has this saying that he says and I just can't figure out what he means. He said it this morning when he was getting into the car to go to school. He asked where his lunch was and I told him it was in his backpack. He then started climbing into the car and said, "Think it!" When I ask him what it means he either just looks at me or says, "You know, Mom." Actually, I don't. So if anyone can help me out, I'd love to know what "think it" means.