Depending on what you're using, there should/may be some extra boxes labelled "piece" "folio" "page".
RG10/523/56/13:
RG 10 is the "series number" (this refers to the 1871 census, RG 11 is 1881, RG 12 is 1891, RG 13 is 1901 etc).
523 is the piece number
56 is the folio
13 is the page
ETA: Where do you have Seleviere from? I'm trying to work it out but depending whether it's a "misheard" or "mistranscribed" name there are just too many possibilities. I really do think that's her remarrying in 1902, so if we can get a better idea of her maiden name + father's name off that it may be possible to track her in French records despite the problems with Paris.