Answer: The DSF Legacy number is the unique 6-digit number your old site contained in the page’s URL that got migrated over during the agency’s Lift-and-Shift initial migration process.

The DSF Legacy fields are only populated when an existing page from your previous website was migrated over. Given that your site migration occurred around end of July 2018, any new page (including Bulletins) you create in Sitecore post that date will not contain legacy data.