It fills all of the current selection slots for you automatically, respecting your saved allergens/dislikes and your "My Preferences" diet-category filter — it's a shortcut so you don't have to hand-pick every meal, and the slots it fills remain individually editable afterward.

Outside of Subscriptions, it only ever picks meals that are free for you at that portion — any meal that would add a charge is skipped entirely, it isn't picked "as a last resort." On Subscriptions, if the store has turned on its "Allow AutoChoose Included Surcharge Meals?" setting, the picker can also fill in a surcharge meal to use up your plan's remaining included-surcharge allowance for that delivery; with that setting off (the default), it behaves the same as everywhere else and only picks $0 meals.