So I may have found the answer to my own question. Right from the Mazda RX-8 2009 MY Service Highlights it lists the cooling capacity as 10.6 US qts for the Series2 MT. The comment I highlighted where they say the cooling capacity was being changed for the 2010 MY likely refers to correcting a spec that was published incorrectly as 9.4 qts for the 2009 MY launch.