Backups & restore points · Managing backup sets and destinations
What does "Delete & start fresh" do?
Short answer: It permanently erases every saved version of that set at its destination and starts a new backup from scratch. You must type Delete to confirm; nothing goes to the Trash or Recycle Vault.
It permanently removes the whole backup history for that set from where it's stored — not just the latest copy, but every version you could go back to — and then starts a brand-new backup from scratch.
Because there's no way back, it asks you to type Delete to confirm. The versions aren't moved to the Trash or the Recycle Vault, and the files on your Mac become your only copy until the new backup completes.
Use it only when a backup can't be recovered — for example a cloud backup whose passphrase is truly lost. To stop backing up but keep the history, use Remove destination (keeps stored versions) instead.