No difficulty is allowed to exceed a score of 18 million points (check this by pressing F5 in the editor to test play the map). If you want your map in the "ranked" category, then you can shorten the map (or replace a portion with a break), lower the difficulty settings (within reason), or remap part of the difficulty. Do not resort to dropping the slider tick rate to reduce score. Otherwise, the map can be "approved". The only difference is that an approved map does not count towards a player's ranked score, but there will still be an online scoreboard.following my previously post http://osu.ppy.sh/forum/viewtopic.php?p=1074116#p1074116
Why not 20 milions or 22 milions ?, increasing the score limit you can also increase the time limit of a map (rule),
2-4 milions does really influence the ranking score?
a lot of times mappers should "destroy" their beatmaps due to total score fault, adding sliders instead of beat or stuff like this