In the Report for Top Recipients (Inbound), the total count of messages with a Spam verdict does not equal to the sum of its individual categories: Spam, Suspect Spam, Customer-Specific spam, Marketing mail, Newsletter, etc.
For instance:
Categories for URL Classification (Customer-specific URL, Malicious URL, Spam URL and Unknown URL) are not included in the report.
This will be addressed in future product release.
Resolution earmarked for 10.9.3 release.