I believe Fences should delete off daily automatic layout snapshots after 3 days. But it won't delete those manual saved layout. For those manual one, what you can do is, to manually delete it off my clicking on it and click on "Delete snapshot" button. Or
You can browse to this folder:
Backups of your Layout/Snapshot are stored in the following directory:
Thank you,
Basj,
Stardock Community Assistant