I'm not really convinced of the translation of "lectio" (litteraly "reading") as "chapter".
It's from modern Latin (also based on Late latin) : Lectio = lesson, Capitulum = chapter. And these meanings are well established in English. I reported that the translation is wrong because Lectio carries a meaning of "something for studying" which is equivalent to a lesson not a chapter which means only a text. Capitulum has also been used since the antiquity for the meaning of chapter.
Mult-as = fem. accusative (direct object) plural
Mut-ae = fem. nominative (Subject) plural
The verb esse (est, sunt) doesn't take accusative. It acts like an 'equal sign' if there are 2 nouns, for example, Puer(Nom.) est discipulus(Nom.). And in this case, there is only 1 noun with the verb sunt. Therefore, it must be nominative and here sunt means "there are xxx".