Memoria de Mario : a deshoras y siempre con Mario Benedetti / Juan Cruz Ruiz. (OCLC #862740886)

This piece has an elastic band around it because it’s not actually bound; it’s just a stack of papers, each folded in half. The current (AACR2) record has the extent as

84 loose folded p. : ǂb ill.

though that should probably be an [84]. The (backs of the) pages are numbered in Spanish words: cuatro, seis, … ochenta y dos (so maybe even [82]).

RDA says to record pages that are numbered in words using their numeric equivalent, so that would be:

82 pages

I would probably mention the loose/folded aspect in a note; some libraries may bind the piece, so it doesn’t seem like an essential descriptor, unless one is doing rare book cataloging. RDA’s “volume (loose leaf)” term appears to be more for updating loose-leaf volumes.