The Available Nights report shows the number of missed nights during a date range. It includes a "# of Nights" columns so that you can instantly see where the big gaps are across properties and date ranges. If you export this report to Excel, this will help you not have to create a formula for that as well.
The grouping will show you the total missed nights per property or owner, so that you can quickly see which property or owner is having difficulty with occupancy.
In the future, we are planning to add actual cost columns to this report so that you can see what the ADG and ADR (average daily gross and average daily rent) amounts are for those missed nights. This will give you a real financial amount to consider in terms of the amount lost by not booking these nights. That's not out yet, but feel free to bug our Feature Request forum about it.