f you have one set with 5 elements and another with 10, the set difference cannot have 13 elements. ------- In anticipation of some possible technical replies

f you have one set with 5 elements and another with 10, the set difference cannot have 13 elements. ------- In anticipation of some possible technical replies, let me be more explicit: It isn't a set difference, no matter how you view it. Viewpoint 1: The original lists of objects are not actually sets because the elements are not distinct. From this viewpoint, it isn't a set difference because they aren't even sets to begin with. Viewpoint 2: There is an implicit "row number" feature of each object so in that sense the objects are distinct and do form sets. From this viewpoint, it still isn't a set difference. If you have one set with 5 elements and another with 10, the set difference cannot have 13 elements.