This setting has two options: Allow Checkout to open dates before today and Allow only checkout to open dates after today (the default, stored value "0"). With the default, every ordering page (A la carte, By The Pounds, Custom Meal Builder, Extras, Packs, Products, Catering, In Store, and more) lists only open menu dates after today even if today's date is still open; with the first option, today's and earlier open dates remain orderable until they are closed. It does not change anything in the admin menu builder, only which of your built menus customers can still buy.

In the current version this option has no visible tab on the Configuration page (/admin/configclient) — its Client Config listing entry exists in the code but its tab assignment is commented out, so a shop admin cannot see or change it there today even though the stored value still drives the behaviour above. If you need it changed, contact Sprwt support rather than looking for it under Client Config.