By design, backups created outside of a defined policy are assigned a "never-delete" state. This means that the backup will not be subject to automatic deletion.

We can import that backup to the policy using the import backup feature, in that way the created snapshot will be added to that backup policy and the retention will be applied.

Go to Policies and select the policy in which you want to import Backups.

After that select the correct filters to find the snapshot which was created manually from the Druva console for example using backup with tags, that snapshot can be identified.