In an RDA record, when page numbers are spelled out in words, record the pagination using the numeric equivalent. For example, if the page numbers go from “four” to “eighty-two”, record the extent as:
82 pages
There are no brackets in this field! Extent of text (RDA 3.4.5) is recorded, not transcribed, so it contains the number of pages with no indication that it is spelled out (though you can mention it a note if it seems important).
A sequence of letters is different from spelled out numbers, though; if pages are numbered with letters (like A-R), record that range of letters:
A-R pages
This is also different from pre-pages with Roman numerals. For example, for a book that is numbered in two sequences i-xi, 1-299, record the extent:
xi, 299 pages
If those Roman numerals are just part of the main sequence (i-ix, 10-299), ignore the that the form of numbering has changed:
299 pages