It lets you dictate the category mix per day for that bundle — "this plan includes 1 breakfast and 2 entrees per day", as the form says. Categories are listed under their category groups with a number box each; the total must equal Meals Per Day.

Leave the toggle on and enter numbers to lock the mix; switch the toggle off (it resets all boxes to 0) to let customers pick any meals. A locked mix is copied onto every subscription created from this price and drives what the customer is asked to choose for each delivery. The Categories column of the price table shows the mix (e.g. "1XBreakfast, 2XEntrees") or Empty.