You get this if you earlier edited the item and did not close your editor/browser while the browser could communicate with the web server - or you are actually actively editing the item.
When you start editing an item, Composite C1 will keep track of the user / item being edited and when the web app is notified about a editor closing, this "lock" will be released again. If you disconnect from the server while editing items and
close your browser, the web app is not informed that you stopped editing the elements.
You should only see this information once for an item - unless you re-create the situation. If multiple users edit the same items the user login of the other user will be shown.
This typically only happen in dev situations, where the web app is stopped before the browser is closed (and items are still open in the editor). If you close your browser first, the messages should go away for good.