From time to time strange messages come up on video sharing website Youtube.com. This particular message comes up in the Youtube creators studio where you can check stats of video, edit video etc. The message came up for me and I don't even have video monetized so I would say this message is a miss report, and not worth worrying about unless the message doesn't go away after refreshing the page.
Monetization data is currently unavailable for some videos. As a result, some information may be missing or inaccurate.