Don't be fooled by the page count in the different format! 171 pages of a more-difficult-to-work-with format isn't a better thing than 720 pages in the format the reader works flawlessly with. It just means that those 171 pages are fixed in format and size and you'll have to shrink them down to see them on the screen.
What size was your font selection when you saw the 720 pages in the lrf format? S M or L? That affects the page numbers.
And I have found that the onscreen display of the LRF files is not accurate to what happens on the reader.
Convert the files to lrf format and be done with it.
And you might be surprised to learn that the files have already been converted to lrf format at
www.manybooks.com or at
www.munseys.com or in the book downloads section of this site, so you might save yourself a lot of effort if you look in those places before doing the conversions yourself.