On Kitchen Locations > edit, each kitchen has weekday checkboxes in five sections: Meal Prep fulfilment, Retail / Wholesale fulfilment, Catering fulfilment, Realtime fulfilment and In Store Menu fulfilment. The corresponding menu pages only list delivery dates on those weekdays (the POS Menu also follows Meal Prep fulfilment), cloning only targets those weekdays, and the customer-facing pages only offer dates on those weekdays. If you untick a weekday later, meals already saved for that weekday stay stored in the database but disappear from the calendar and from customers' choices until the weekday is ticked again.