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My guess is that intent is to take 0 for absent weeks. We want to take into account attendance.

A 0 is averaged into your average, you don't go to 0 for one missed week.

This means that it is possible for some members of the council to not be present a given week.

I meant not to drop it all to zero , just taking the level ( or rank ) of the absent week as zero in calculation. I think you meant the same too.