Hi Moumita,

The cutoff marks and the minimum marks required to get into a good medical college of a particular state varies year to year according to the pattern of the question papers and also the level of difficulty. if the paper is above average the marks required is not significantly high. however in case of an easy paper you will have to score really well to get ahead of the competition and get admission in a good college. so you can never be too sure. however, being from sc reservational category, if you keep your score above 500-520+ there is 90% chance of you getting a very good college in your state if not the best ! so keep your aim high and work hard accordingly ! 

Hope this helped ! All the best for the upcoming exams ! :)