In the parish records for Kirkheaton, West Yorkshire, some of the early 18th-century records have an "aff." notation at the end of a burial record (Ancestry.com example). I presume that means that the writer of the parish register received affidavits that the burial took place, rather than presiding over it himself.
Some of these notations have a number after them, as in this case of the infant son Thomas of one Joseph Jubbs of Whitely. You can see the next entry also shows a similar notation, with a 15 rather than a 12, for William son of Thomas Deison (sp?) of Dolton.
So I thought maybe it was the number of days the child lived, until I saw the same notation for the burial of an adult, incidentally for the same Deison family.
So I thought maybe this was the number of people who attested to the event, which took place in private burial grounds. The families concerned all seem to be located in villages within the parish but not near the parish church.
Does anyone have any information about what these numbers might mean?