How does “Locked in Xero and the deletion lock” work on the Signed Accounts page?

Filed accounts over books that can still be edited are a risk, so the table above the shelf reads both of each company's Xero lock dates and holds them against the latest year end filed here, marking any final year whose lock does not reach it and counting the lines dated inside a filed year that reached Saral after the signing. The deletion lock is the other half: switched on in Accounts → Settings → Document Protection, it refuses every delete on this page and says so at the top, so inert delete buttons never read as broken. Anyone may lock; only an Owner unlocks, with a reason. Where: Signed Accounts (/accounts/signed-accounts).