Currently, the Dock icon of SpamSieve shows the number of good messages. The Dock icon of Apple Mail shows exactly the same thing. The SpamSieve count can be turned off in the Notification tab of SpamSieve Preferences, and the Apple Mail count can be adjusted in its Preferences.
My suggestion is to add an option for the SpamSieve Dock icon to show the count of unread messages in the Spam folder, as a user-selected alternative to the count go good messages.