Those are not two different explanations. They're the same explanation, with differing levels of stated details, intended for two different audiences. One is from the student guide, which aligns to the instructor-led presentation of the class. The other is from the online self-study course, for which there is no instructor, and so the content is presented more explicitly. The instructor would be explaining the content and working through the example in an instructor-led class.
Arguably the examples in the student guide could be reversed to align with the way the material is covered in the self-study lesson, but that doesn't make the explanation different.