What shocking text does Toby get from Rachel in Section 1, and how does he react?

In Section Pne, while Toby is looking through his dating app pictures and messages he finds a text from his ex-wife Rachel. Rachel tells him that she had to leave for Kripalu early and had to drop their kids off a day early. She let herself into his house at four o'clock in the morning and left the kids in their room. Toby is shocked that she would do this, and he calls her to tell her that it is unacceptable. Rachel is unfazed and does not see what the big deal is.