In the current version /admin/datebuilder is a leftover developer sample rather than a customer tool: it prints a fixed table of Monday-to-Saturday dates between 4 June 2018 and 4 June 2021 with Copy / Excel / PDF export buttons, and it does not read or write your real delivery dates. It is not linked from the admin menu, and notably it has no login check at all — unlike every other admin page, it can be opened without being signed in. It's harmless to ignore — it doesn't touch your data — but flag it to Sprwt support if you'd rather it be removed. Real dates are generated as described in "How are delivery dates created?".