To add to what mabela has already said, what normally confuses people with the Volume Capacity number is that it includes the total of all volumes - including snapshots.  So using your example, you probably haven't actually configured 8.777PB of volumes - but if you add up all the volumes AND the snapshots that you've got (including those taken by things like RecoverPoint) you'll find that the total capacity is that number.
Hi All,   I understand what is physical capacity and even there is a standard XIO table showing for a 40TB, 6 brick cluster the usable (physical) capacity is 183.33 TiB but what is Volume capacity and how it is calculated? Can any of explain it to me please?  [IMAGE]
XIO - Volume Capacity