The prediction of marks for scoring rank less than 500 is quite difficult. Firstly, ranks in KCET depends on your board marks as well as KCET exam marks. Try to score at least 90% marks in Boards and any marks between 150 to 160 in KCET, can fetch you a rank within 500. But these is just an approximation made on previous years analysis and the actual marks depend on the difficulty of paper, no. Of students etc.