Submit a missing stay request 10 days after the stay completed. Unfortunately this happens extremely frequently with foreign locations and the exchange rate. Its like they have the conversion backwards. In your message, state that you received the incorrect points for the stay, and that the conversion was 1 (local currently) = xxx USD and you are missing yyyy amount of points.

Same happened to me at a property in Barcelona several months ago - Stay was around 800Euro before taxes, but I only got credited on something like 700USD worth instead of ~920USD.