The 'High Scores' window shows all the high scores of the current piece by all users. The 'Individual High Scores' section shows the high score of each user who has practiced the piece. The 'All Users' High Scores' section shows the high scores of all users (a single user can top score more than once). You can reorder the columns using the header of each column.
High Score items show you information about the high score practice sessions. Items with a green/yellow play icon next to them have the recording of this practice available to listen to. A green icon means that the practice recording is saved in the library permanently, whereas a yellow icon means that the recording is saved in the library temporarily. A grayed icon means that the recording is no longer available. Double click on an item to see its Performance Report. Right click on an item to see further options.