F-SECURE ANTI-VIRUS FOR MICROSOFT EXCHANGE 7.10 Administrator's Manual page 269

'spam-scanner-instances' (oid=1.3.6.1.4.1.2213.18.1.35.500)
has been set to 5.
To take the new setting into use, restart F-Secure Content Scanner
Server.
IMPORTANT: Each additional instance of the Spam Scanner takes
approximately 25Mb of memory (process fsavsd.exe). Typically
you should not need more than 5 instances.
Administering F-Secure Spam Control
CHAPTER 9 269