Hello Ouria,
It is a common misconception that the PMP exam is testing what is in the PMBOK Guide. That is not the case. The guide is the primary reference for the exam, but you will see questions on the exam that come from sources other than the guide.
The complete knowledge that you may need to know for the exam is covered in the PMP Exam Content Outline which you can download from
www.project-management-prepcast.com/pmpoutline
This is why The PM PrepCast not only covers content from the guide, but also includes additional lessons that cover the 'other' material. So any lesson that numerically 'doesn't match up' with the chapters in the PMBOK Guide is is such an additional lesson.