What are the +/- numbers near the title and artist (ex: -1 or +2)?
This means you previously boosted (+1 to +9) or cut (-1 to -9) the play of the song or artist. You can increment this number by one each time the song/artist plays. The higher the positive number, the more frequently the song/artist will play. The lower the negative number, the less often it will play. If the amount is zero no indication will appear.