downloaded the cap and tested it with 997.
edit: now I get it.
Item.Count is picking an object to refer to from the Item family. Then it's applying the Count function on it. So it's 1.
In order to get all the instanced objects in that family, you'll have to ask for each and sum them all. Note that you won't be going through each object TYPE, but through each object INSTANCE. So, add 1 for each.
-global('sum') = 0
-global('sum') = global('sum')+1
there you have the total of instanced objects.