It can be helpful to get an overview of how many instances of each type are present in the Revit model:

• Go to the Configuration section.
• Add property.
• Select Function.
• Select Type as Object type; Function properties are only applicable for types.
• Select Count Objects.
• Give it a name and Add.
• Now go to the Manage section and add the new property/column to the Object table. 
• You can now view the number of instances for each type represented in the model(s).

Where: HOME / <project name> / OBJECTS / Configuration