supersedure cells are usually very few, bees tend to position them at the extremities of the cluster where the queen seldom visits -as the cluster is three dimensional and basically spherical the edge of the cluster may well be at the side of the frame not just in the middle of the end one.
Bees 'tend' to put swarm cells at the bottom of the frame, but then again, I have seen just as many hives with
ALL the cells ranged on or just under the top bar - what label do the books tell you they are?
as soon as a colony swarms you will also get the panic building of emergency QC's wherever the bees can find a suitable larvae so the labels in all the books goes out the window.
Basically, if the colony has swarmed by the time you inspect, they are
all swarm cells regardless of where they are (I saw some clown not long ago profess that in the case where cells are found in the middle of the frame after swarming then the swarm was triggered by the bees building a supersedure cell and getting carried away!!)
If you inspect and there are QC's all over the place and the queen is still there - they are
all swarm cells.
If you inspect, the queen is still present and there are just very few QC's in the classic 'supersedure position' they may be superseding, but then again they may be planning to swarm.
If you inspect, the queen is present and there is only one QC (or a couple, close together and the same age) The probability is they are trying to supersede.
But they may well swarm