<p>You can actually chose to take Chinese on Oct. 14 because you're registered for the Math IIC test. Just take the test on that day, and it will be scored normally.</p>
<p>Here's what Collegeboard says (<a href="http://www.collegeboard.com/student/testing/sat/testday.html):%5B/url%5D">http://www.collegeboard.com/student/testing/sat/testday.html):</a>
"You can change your mind on test day about which Subject Test you want to take. You may substitute a Subject Test (other than a listening test), or add Subject Tests (other than a listening test) on test day."</p>