In the past songs like The Big Black have been downscaled bpm wise for the reason that both the osu! logo on the menu screen and the Kiai flashes in the game would pulse like crazy with such a high bpm (so much that it might require an epilepsy warning which is obviously not possible in the menu). For that reason the map had been changed to use 360 instead of 720bpm.
Stuff like this can still be addressed when you get a BN to look at your map though so don't worry about it for now if your song is actually 999bpm.