Listening to boys and their potty talk is interesting. So just in case you ever hear the phrase "I'm going number 3!" around here, I thought I'd share S's explanation that he gave to J today. I'll spare you the rest of the conversation. You are welcome.
Per S: "J, If you need to tell anyone what you are going: Number One is pee, and Number Two is poops, and Number Three is toots."
So now you know.