There is no standardized way of displaying page numbers, many ereaders follow Adobe's 1024-characters role model, Kindles don't show any unless a Real Page Numbers map is included, and very few actual EPUBs include the
Page-map which in theory should obviate the need for all the guesswork. I have no idea how calibre calculates it, knowing the development model it probably uses some standard the IDPF came up with but everyone else ignored.
Personally I would just go with chapter numbers and a quote, difficult to mess those up. In fact, the academic world has more or less decided to go with that, and who would know better than they.
