Well, most likely, for one show (once upon a time) you reserved three tickets and only used two, or you reserved two and only used one. At any rate, you used less than the number of tickets than you reserved. So, even though you DID show up, you didn’t get FULL credit because you didn’t use ALL of your tickets.
That’s my guess. If you don’t see a “Did Not Attend”, then that’s really the only possible explanation. Unless our computer forgot math…which is unlikely.