Ingredients with negative quantity

It is also possible to deduct a negative quantity, e.g. for situations where you sell a pizza with toppings and the customer does not want any of the toppings. Normally you sell pizza with ham, but the customer does not want ham. Therefore, when selling this pizza, you need to keep the stock of ham unchanged after the sale. You can do this simply by creating a "No ham" product and setting the ham deduction for it to be the same but negative amount. This way, when the pizza is sold, the ham is first deducted, but by charging the "No ham" product, it is also stocked. The stock quantity of ham is therefore not changed by the sale.