He saw that he was a girl, of course.
Or rather, he saw his breasts, and figured out he was a girl, but it was pretty much the same idea.
Linda, of course, was shocked upon meeting him, and he had to explain that, first of all, he really was Jon, and second, Why he was a girl, and though he liked Linda he wasn't sure he could trust her, so he made up a lie.
"When I was 14 I realized how much I wanted to be a girl, and for a while I would dress up like a girl for myself, but finally I told everyone. And On my 17 birthday I got A sex Change and breast implants"
"Wow I never would have guessed you were like"
"Neither did I" Jon answered "Oh and karyn got implants too and she died her hair blond
"Oh wow You both have really changed Why don't we call karyn and we can go do something It's gonna be so much fun now that we're all girls."
"Yeah" Jon knew he would have to act like a real girl out in town to prove that he really (not really) was a girl