So that's where the links in the storage capacity panel comes into picture.
Each of those link give details about each kind of object like, volume,qtree,lun or aggr.
And further, the reports give more info on each kind of space management like,
thin provisioning ie volume guarantee
Overcommittment @ volume level for qtree/quotas,
look at volumes-quota-committed
and overcommittment @ aggr level for none guarantee volumes.
look at aggregate-space-summary report
So there are report for each one.
So BTW is there any specific calculation you are looking for ?
Regards
adai