Duplicate files · Scanning and Auto-scan
Why did I get a "Duplicate files found" notification?
Short answer: A scan found at least about 200 MB of duplicate copies, so Storage Studio posts one summary notice with a Review duplicates button. It's never one per file, and it clears when you open the list or clean the total below that level.
A completed scan found a meaningful amount of space in duplicate copies — at least about 200 MB — so Storage Studio posts one notification in its notification centre, such as "Duplicate files found — about … can be freed", with a Review duplicates button that opens the Duplicates window.
You get one summary notice, never one per file. It clears once you open the list, or once cleaning brings the total below that level. If you'd rather not see it, switch Auto-scan off so scans only happen when you ask.