Thanks for posting the screenshot, very helpful.
According to the screenshot, you have version 31.0.0.122 installed for Firefox/Safari. This is the most recent version, released on October 9.
You also have version 31.0.0.108 for Chromium-based browsers (e.g. Chrome, Opera). This is not the most recent version, and thus the reason the update notification displays, as it is prompting you to update this version of Flash Player. Once you update this version, the notification updates will stop.
Note that notification updates only update one version at a time, therefore, user's who have both NPAPI and PPAPI installed will receive multiple notifications. Notification updates can also take up to 7 days to notify a user that an update is available.
Background Updates (the 'Allow Adobe to install updates (recommended)' option), updates ALL Flash Player types (NPAPI, PPAPI, and ActiveX if on Windows 7 or below) within 24 hours of the new version being available. This is why this option is marked as the recommended option.