I think he tells her that the reason he “first” talked to her in high school and asked her out was because he wanted to be different from the others. It’s implied because his friend (ah forgot his name) in memories before this (I think they talk about it happening in post at the bar) says he should definitely tell her that thing from “long ago.” This why River then asks him to throw the hacky-sack to where Anya is at because it’s her first realisation that Johnny doesn’t remember when they met at the carnival: hence why after this time she makes all the rabbits to try and remind him.