When you open a product's detail view, you'll see a table showing the history of all operations involving this product.
This table includes all purchases, adjustments, production runs, transfers, sales, and inventory audits for the product. The sum of all values in the "Quantity" column equals the current stock level of the product.
By clicking on "Product creation," you can adjust the initial stock level that you specified when creating the product. By clicking on "Adjustment," you can also modify the value of that adjustment.