Jake, are you talking Commsec IRess? or just standard Commsec Web.
In Commsec standard Web says:-
As at 3:30 PM Trades 344
Vol 9,817,109
Where did u get your:-
Volume 12,122,421
trades 621 .........as at 2:29:31 PM
from?... Guess its a combo of Chi_X & ASX? yes