stock quantity vs sales order confirmed quantity

when creating a sales order for a particular item, the system confirms quantity 100 whereas when i check the stock status of the material using any inventory report( e.g.. mmbe, mb52), the system shows 200 of the stock in unrestricted use.

When I simulate the material requiremnets using ATP quantities, the system shows a previous sales order against which quantity 100 is shown as confirmed. However, when I checked that particular sales order, it is already delivered and invoiced(hence it should not be shown in the ATP quantities).

Can anyone please help me and suggest what is wrong here? it is very urgent.