Cancel OT Order (Partially) / ST is sales updated

Dear All,

Appreciate your inputs on the below scenario.

ST / OT is raised for an item A with quantity 100.

ST is sales updated for the entire 100 quantity.

OT is yet to be received ( out of 100 Qty, 60 is moved into stock and 40 in Transit Stage)

Now we need to cancel 40 Qty as those quantities are not shipped to our warehouse.

How to achieve the above.

Thanks in Advance.

Regards,

Basith