This is one of the first things Jack hears a person from Outside say. He doesn't understand that the "little girl" is him. People with long hair Outside, like Jack, are usually female, especially little kids.

This is something Jack overhears another cop say to Officer Oh. He doesn't understand what it means, but that's okay. The cop doesn't understand Jack, either. He's the first of many people in society who aren't going to understand what Jack and Ma went through but are going to make assumptions about it anyway.

The more knowledge Jack gets, the more he thinks he knows everything. He doesn't yet have the knowledge to know that he will never know everything.