Here's how it could be. In practice what happens:
decide which product to manage in stock, quaesto is added to in a list of products with the search field. the fields are name, quantity available, quantity understock, purchase price, sale price, a field where you can enter as many quantities upload or subtract from the warehouse and then a pattern of movement, made supplier, customer made, purchase, movement in and output. a bit like the screen to change the prices of products, it should be similar, but in this case we changed the amount of stock.