With Yes (default) the meal-selection page shows a Random button (with a refresh icon). Before any meals are picked for a delivery it fills the empty slots with random eligible meals. Once meals are already selected, the same button appears again in the page's action bar whenever the plan allows swapping meals (whether or not it also auto-selects meals for the customer) - clicking it there clears the current picks and randomly re-fills them, i.e. a swap all meals action. Set to No to remove the button and make customers pick each meal manually.