It could be, for example CSV values.
Username, Score, Endurance Time.
user000001, 12, 8329
user000002, 17, 12329
user000003, 8, 3593
...
user999998, 5, 589
user999999, 12, 10384
Sort by highest score. Endurance time as a tie-breaker.
If the score is the same, the highest ranked user is the one with the highest endurance time.
Anyway, I'm starting to realize I really have to take the "database-on-a-server" path.
My initial idea was to have my game downloading the entire scoreboard, updating it, sorting it, displaying it and re-uploading it using lists.
This could be fine for a few dozen users, but if I ever reach thousands, I guess this system would break.