This option makes SpamSieve show the number of new good messages in its Dock icon. If there are no new good messages or if SpamSieve or the mail program is frontmost, SpamSieve will not show any number (rather than showing zero). Clicking the Dock icon, activating your e-mail program, or training SpamSieve with a message will reset the count.
The slider lets you control the size of the number in the Dock icon.
If you’re using DragThing 5.3 or later, SpamSieve can show the message count in its tile in DragThing’s process dock.