Some of the message processing numbers shown on Dashboard and/or Reports do not appear to match expected message count numbers. The totals for the various threat categories may exceed to total number of messages processed by Messaging Gateway (SMG).
This is by design. The Status Dashboard displays statistics based on the number of threats, not the number of messages.
A single message with multiple threats causes the count of a specific threat category (Spam, Content, Malware, etc) to increment by the number of threats in that message based on the number of verdicts it gets.
For example, the following verdicts make up the "Spam" threat category:
So if a single message triggers both the Sender Authentication policy and some other Spam policy, the Spam threat counter on the Dashboard will be incremented by 2 as this message contains 2 threats.
For more details, please see in the following topics in the Aministration Guide: