If you purchase a backing track with a START license, you will be able to publish the derived song (from the backing track plus your voice) up to 20,000 streams on stream platforms (spotify/applemusic/amazon) and 20,000 youtube views.
If you buy a GOLD license base you will have a limit of 200,000 streams and 200,000 youtube views.
If you buy a base with UNLIMITED license you will have no limit of streams and youtube views.