In the table the column is labeled “Registre et feuille” which translates as “register and sheet,” although “folio” might be a better translation. I would take “registre” to be a volume number and would expect it on the spine or title page of the volume. Each sheet or folio in the volume gets a number on the front only. For “feuille” the record could be on either the front of the sheet (recto) or back (verso).
I would expect the volumes of baptisms, for example, to be consecutively numbered, but that seems not to be the case. Perhaps other volumes of records, marriages, deaths, confirmations, and so on, were given register numbers in the sequence.
