This Odoo 9 Enterprise app helps to see the available stock on Pos Interface.
Which helps the salesperson to order for less qty available item to purchase department, Control the sale of the item when it is out of stock etc.
The screenshot above is in Odoo 9 Enterprise where round circles show the available physical qty of the item / product.
When the sales person picks the item, it automatically reduces the qty on time. Similarly If the sales person remove the item from order list, it automatically increases the pos interface.
The second image shows the selected items and remaining qty on items thumbnail.