It wouldn’t be uncommon to have a dozens signs that all look the same when done by your baby. Babies have very poor fine motor coordination. Some toddlers even carry this into childhood and by the time they reach school aged, are still struggling to control their fingers and hands the way they’d like to. ASL is not designed for babies at all. Some early sign programs stressed this and modified signs so that babies can do them easier. However, more recent programs, ours included discarded this in favour of learning a real language ASL.
The reason we do this is because it’s used around North America and so your baby will be understood by more than just his family. Since there isn’t a universally accepted baby sign language, then it’s the best we can do. That means some signs will look very similar. Arms flapping can sometimes take on the meaning of more than 20 signs! What should you do? Well, there’s not much you can do. If your baby really thinks he’s doing the sign, and does it each time he sees the object or hears the word being said, then to him, he’s doing the sign properly! My advice is to just continue to do the sign correctly by modeling it for him. Eventually he’s going to do it right. My second piece of advice is to look to the context in which signing is taking place as this will help you discover what your baby is singing about.