I guess so - how many lines do you see in the Tracking center for August?
A few things to note:
* /var/log/mail.log is rotated weekly (not monthly)
* status=sent can happen/will happen multiple times per mail, which gets passed through PMG - depending on configuration - the listening postfix takes the mail and hands it to the pmg-smtp-filter - once this is accepted it adds a logline with status=sent, and pmg-smtp-filter passes the mail to a postfix which sends it out - which also adds a status=sent line...