Some models are grouped together, as its the case for Mixels http://brickset.com/sets/5003799-1/Mixels-Series-1-Collection
This is quite handy for when we have all the sets, because our "owned list" can be very long due to these small sets. tickthe "VPC" items reduces the size of the list. The problem is that the parts and the number of sets owned are not included in the collection summary (simple or extended).
Another example, i have the entire CMF simpsons collection. I tick this item: http://brickset.com/sets/71005-17/LEGO-Minifigures-The-Simpsons-Series-Complete
and here the parts are included, it's very convenient.
So it would be nice if that could be the same things for Mixels or other VPC's.