Unfortunately, it isn't as simple as that.
I hadn't noticed it on my Libra H2O when reading some purchased kepubs, but, then I realised that I had the book progress set to percent read

I have been using page numbers for the chapter, percent for the book and could see the full book page when the progress slider is displayed. The previous testing was done on other devices that I did have the page number in both places.
So, last night I changed to page at the bottom and checked. What I found was that book page numbers change at about 80% of the rate of the chapter rate. Every few pages, the book page number wouldn't go up. The chapter page number changed every time I turned the page.
I don't have any patches installed. It doesn't seem to be a font size, as I tried a couple and it happened for all. The rate of mismatch might be different, but, I haven't tested enough to be sure.