That means your version of the album is not what Plex recognized, or is not what is up on Musicbrainz.org
If you want Plex to follow your embedded meta tags much closer, you need to tick that check box.
But that means that all your files need complete and correct tags.
The alternative is to look up your music on Musicbrainz and help Plex identifying it by embeddding the Musicbrainz ID as meta tag.
Musicbrainz Picard can do that for you. [HowTo] Music Organizing with MusicBrainz Picard
