This question has been posted awhile so I’m not sure if you have solved it.
I think what you need to do is set your Data Source to 'Search for Items :group by ’ and set the field to ‘Items’ with grouping ‘Exact’ (only if the item type are the same i.e. car is car and not Car or CAR) and set aggregation to ‘Count’.
Value Expression would be ‘Current’s point count’
That should get what you need