The Prenap(s)
I'm not sure I fully got it. Right after the wedding, CZJ tears up the prenap and GC doesn't really mind. Then he realizes he was fooled. At the end of the movie, he signs The Prenap again and hand it over to CZJ to sign it too and she tears it up again. Suddently it is a huge breakthrough and proof of her love.
Could someone please explain it to me thoroughly? I may be dumb.