Having finished chspter 53, with 2 chapters left to read, when I put my Kobo to sleep I am apparently 44% of the way through the book - The page list for the print version says I'm at 82%.
This has been a fun and interesting exercise in trying to figure out the mystery of the maths, but when it comes to the Kobo stats I know neither whodunnit nor how. As shown above, it's not a complex book in terms of layout, all text, and lots of it. It will be interesting to try a de-drmd epub version in KOReader to see how its measurement of progress stats compare.