They limit how many upcoming delivery/pickup dates a customer can see in the date picker on ordering pages:

• Calendar Visible Date Range: used by A la Carte, Packs, Catering and most modules.
• Calendar Visible Date Range - By The Pounds: for the By The Pounds (proteins by weight) module.
• Calendar Visible Date Range - Custom Meals: for the Custom Meal Builder.

Enter a whole number of dates. For By The Pounds and Custom Meals a blank or zero (or negative) value falls back to 7 dates. Dates that are closed or past cut-off are never shown regardless of this number.