Self is a dimension of The Elevate Formula, which is Skill 5 of The 7 Skills to impress™, described in Part 2, Chapter 5 of the book.
It refers to how people see the source of either their strengths or problems as being associated with their Identity.
A High Score Identity person sees their strengths as part of who they are (Self). However, they regard problems as not being part of who they are, i.e. Other. It is the opposite way around for a Low Score Identity Person.