That's true, Chris, but when they talk about "a conjugated verb" in this, and other lessons, they usually mean a pronoun/noun followed by a conjugated verb. So that's not the explanation.

But in the first section you'll see that there is always a comma after the phrase, so it's not directly connected to the verb, e.g.

"Le lendemain, j'allais m'inscrire à l'université."

"The day after, I was enrolling at university."

You can't use "le lendemain" to say something like "The day after I enrolled at university I met Paul."

Actually, le lendemain isn't followed by a verb in the lesson examples. If you look carefully you'll find it is followed by a personal pronoun.