The cause for this mismatch is due to a slight difference between the edition of book that you are using the edition that we used originally when matching up the sections with the videos. They should match up the large majority of the time, but in the rare instance that they don’t, I’d recommend simply reading sections that do match up and saving the ones that do not for a future lesson that more directly relates to the topics in that section. For more information regarding how we matched up the sections of the content review books with the videos, please feel free to check out this article.