Hi David, This is a bit different from the collections question that came up yesterday, has a similar answer:
no, collections (e.g. documents) cannot be aggregated (e.g. SUM, MAX, etc.) at a higher object level (e.g. task)
you can, however, create a Document report with a COUNT on any numeric column, then Group it by Task to get the total Count per Task at that (blue) grouping level
alternatively, I invite you to consider our "https://store.atappstore.com/products/all/" UberCalc solution, which does allow you to create and maintain such aggregations (among many other uses)
Regards, Doug Den Hoed - AtAppStore