The problem with the hash-marks on the Kindle's progress bar is that it depends heavily on how the ebook creator chose to build things. They can be completely non-existent (getting somewhat more rare, but not unheard of to be lacking an NCX file), or the ebook can be divided into sections/parts (with no individual chapter points), or even "books" in an omnibus-type ebook. Different NCX points can also be nested, and lurking, for those who suspect, but not available graphically for those who don't.
Those points are certainly
most often used as "chapters," but there's no hard and fast rules governing that. Sure, it wouldn't be impossible (or even difficult) to have an X "pages" until the next ebook-creator-inspired NCX point on the Kindle. It just might not always be a "chapter."
