The left-hand side in Inventory shows the actual stock. For each product, you will see the calculated quantity. This is based on the balance, supply/disposal and consumption. To understand the calculation, please refer to the 'Stock details' report. 

If the stock is not correct, this could have several causes. You can check whether all sprayings and fertilisations have been entered. You can check whether all delivery and disposals have been recorded. You can also choose to add a new Balance . In fact, you can also enter a balance in the middle of the season.