Hmmm, sounds like poor technique. In Australia we aren't allowed to assign more than one level for that very reason, to prevent confusion.
Had you requested FL190? Were you inbound and approaching your descent point? If so, it sounds like you were given your request, and the controller was also giving you a further "when ready, descend FL120", thinking that when you reach your profile descent point, that you'll leave FL190 and descend FL120. If the clearance to "descend FL120" was re-stated, either the controller realised their error, or a trainee was on and the instructor corrected the trainee.
But then, I'm only guessing. Need more info.
