If a snapshot on the source volume has recently been removed and the snapmirror hasn't been updated, then the destination volume will contain the original number of snapshots.
On the other hand, the source volume may contain a snapshot with 'Snapmirror' at the end, if it is in a relationship.
Hope this helps!
The destination volume in a relationship replicates the source volume in terms of data, snapshots and settings.
This will update on the destination, once the snapmirror transfer has completed.