Enable Finding Deduplication will turn on the Deduplication Algorithm for all Findings. Deduplication will be triggered on all subsequent imports - when this happens, DefectDojo will look at any Findings contained in the destination Product, and deduplicate as per your settings.

Delete Deduplicate Findings, combined with the Maximum Duplicates field allows DefectDojo to limit the amount of Duplicate Findings stored. When this field is enabled, DefectDojo will only keep a certain number of Duplicate Findings.

Applying Delete Deduplicate Findings will begin a deletion process immediately. DefectDojo will look at each Finding with Duplicates recorded, and will delete old duplicate Findings until the Maximum Duplicate number has been reached.

For more information on how DefectDojo determines what to delete, see our guide to Deleting Deduplicate Findings.