It is $688 for this ring semi mount without 2.02ct（9.85 x 7.02 x 4.60mm） oval center stone, with no bigger than 2.5mm round lab grown diamond in 10K gold.
The credit from return #26829 is $265.19+$88.52=$353.71, so the price difference for the replacement semi-mount that you need to pay is ($688*18%)-$353.71=$210.45.