Thank you for your input Harry. It is a good thing that you that you (as always) are happy!
Chapters are great for references and can be pretty precise, particular in textbooks. But it has its limitations for some text types.
Kb can be used to say something about the length of a text but will not work between various text encodings and is useless for books containing graphics (as all books do – at least for a front page). In addition most ebook formats compresses the text files. And my ebook reader do not tell me the size of the file.
Implementing functionality allowing fail safe cross referencing and giving information about the actual length of a text is very simple from a programmer’s perspective. The difficult part is agreeing on some standards.
Page numbers varies between various editions of books, that is true but that is maybe something that can be solved in the new world of digital reading.