This table shows how your ACT score will rank you against your peers. It makes sense that a 36 would put you at the top with 100%, but it is interesting to see that a math score of 34 or 35 scores you at 99% and a score of 30 puts you in the top 95%! So, if you have scored 30 or above you have probably already scored well enough to impress most colleges.

While scores of 30-36 are nearly all the same percentile, it is a huge jump to change your score from a 20 to a 28! Making such a large improvement is equivalent to moving from the 55th percentile to the 91st percentile! So, set reasonable expectations. Do you really expect to move from the middle of the pack at 55% to the top 10% by studying just a couple hours? It will take LOTS of practice and probably lots of tutoring to make a large improvement like that, so set aggressive, yet realistic goals and work harder (LOTS of practice) and smarter (get some tutoring) to achieve them.