Hi Suhas,
That means, there is no issue with the actual cost calculation for activity types. I wonder if you are referring to the PO settlement here. You can double click on the item that is offsetting all other cost elements. I hope it is PO settlement. once the settlement is done, the order balance will be zero.
If I understood your issue incorrectly, please send the screenshot of PO cost analysis.
Thank you,
Srinath