If you take a look at the suggested schedule the organizers put up on the IS site at
http://infinitesummer.org/archives/168 , you will see that the basic design is that it is the main text that determined the landmarks, with the footnotes being a variable extra number of pages per week. Of course, it's just a guideline, but if you are trying to figure out where the site is getting its percentages and how it is determining spoiler lines, that is the reference. I suppose the bookmark (
http://miklb.com/infinite-summer-bookmarks ) isn't that helpful on the kindle, but the guy who made it did a good job, so you could do worse if you needed a reference for pagination that you could scribble your latest paranoid musings about the entertainment on.