this is difficult

Think of it like this:

Students can only be cited as "late" if he arrives more than 5 minutes past the last ring of the homeroom bell. He arrives 17 minutes past the last ring of the homeroom bell.

If they do not state that he has been properly cited as being late then this isn't a valid argument BECAUSE he could be a teacher (therefore that rule wouldn't apply), he could have a pass because he stayed late to finish up a test in another class, etc. SO unless they say "he has been properly cited as being late" then you cannot make a valid conclusion that he arrived more than 5 minutes late to the last ring of the homeroom bell.

Think of it like a concert or an amusement park. Superset is like the general admission ticket and subset is like the VIP access or fast pass. You still get into the concert or amusement park by having general admission to enter even if you don't have VIP access to do certain things or get on rides faster. So having the VIP access/fastpass isn't necessary to be in the concert/park but you can have the exclusiveness and still be considered someone attending the venue.