Sign language flubbs

So, Matt and I have been trying to get Ethan to use a little sign language to tell us what he wants, thus reducing the amount of fussing that goes on. One that he has REALLY latched onto is the sign "finished" . It used to be that when he was done eating. he'd just wine until we got him down from his high chair. Now when he's done eating, he just makes the finished sign, which is great fro both parties. He gets down from his High chair like he wants and mommy and daddy don't have to put up with a lot of fussing. I don't think he quite understands exactly waht the sign means though. The other day, I took Ethan to the graocery store with me to pick up a few things. I put him in the cart and strapped him in. Being the active little boy that he is, he really doesn't like this arrangement. Instead of crying this time, though, he simply gave me a dirty look and did the sign for finished. I guess the sign language still needs a little work.