You can view the score earned for playing a song in the song summary screen. As an example on the screen below you can see that
- 33900 is the previous highest score for the song;
- 40600 is the new high score of the latest performance of this song (all parts).
The number shown on the Leaderboards (41400 in this case) is a combined score - the best result of all parts previously played.
Once the song is relaunched, the new High Score of 41400 will replace the previous value of 33900