The variance adjusts for historical corrections (for example entering a death, etc) that occurred during the recapitulation period. There are a few other items that can cause this:
A member who demits AND dies in a year can only account as a single negative event, not two.
Any time an event's AR year is forced, this will cause a variance because the bottom line number has effectively changed on a prior (certified) report. This can include any 999 corrections.
The bottom number is the significant number - if that is correct, the secretary should know that any variance is due to corrections in the member records since the last annual return.