Spam statistics - why so many not checked

[Al Crowley]

One of our customers complained that a lot of spam was making it to his inbox. We have spam assassin installed and running so I was checking through the settings on the control panel a bit. On the statistics page I noticed that 96% of our mail is listed as "not checked."

Does that mean that spamassassin isn't being run on most of our incoming mail? If so, what can I do to fix that? Any pointers will be much appreciated.

Thanks,
-Al