They are added when your kitchen finishes the delivery day on the admin Dashboard (the Finish action on a closed date). At that moment Sprwt totals every meal the wholesaler bought for that date that is not refunded or already marked delivered and adds it to the wholesale location's on-hand stock as an Add movement, so the wholesaler sees the new units under My Wholesale > Stock Management and can sell them through Grab&Go. Until the day is finished the stock does not change.