Say you were to book a 12 segment OWE in First (for which you paid $6000) and then terminated your travel after 2 segments,they would refund the difference between the $6000 and the A-class one-way value of the 2 segments already completed and then take off a further 10% of the remaining value.
So if the published A class value of each of your completed segments was $2000, your refund would be:
6000-4000) = 2000. Now they would take a further 10% off this so you would get back $1800.

Salt.