When you upload music on Subvert, you choose between two options:
Upload Track For single songs or standalone tracks. Use this for a one-song release - a single, a standalone B-side, or any individual track that isn't part of a multi-song release.
Upload Album For any release with more than one song - full-length albums, EPs, or two-song releases. Even if your release is small, if it has multiple tracks, use Upload Album.
Not sure which to choose? If it has more than one song, it's an album upload.