At this time there isn't a method to see the actual size of a snapshot from the host side due to the size of a snapshot being dictated by the changes made to the blocks locked in the snapshot from ONTAP's perspective. The math gets even more convoluted when a block is locked and altered in multiple snapshots, allowing you to restore to the multiple versions of the same file. Another thing to mention is the total "currently" used space for all snapshots listed in "df" from ONTAP doesn't fully reflect the size consumed by all the current snapshots until any recently deleted or auto-deleted snapshots finish going through the "block reclamation" process, which is an automated background task.
