The spacemon snap_reclaimable command displays the space that can be reclaimed by deleting a Snapshot copy.
sdcli spacemon snap_reclaimable -f Storage System -vn Volume Name -s snapshot
Storage System is the name of the storage system on which the volume exists.
Volume Name is the name of the volume on which the Snapshot copy resides.
snapshot is the name of the Snapshot copy for which you want to view reclaimable space.