Hello aspirant

59% in xii Science, it means you got approximately 60% . If you do well in your all 4 Academic years and get good percentile in your all four years of b tech, no one will stop you to get a good job in reputed Companies like Google, Amazon etc . No doubt while placements are provided your x and xii marks are also considered. That is only for reference. It doesn't make any sense to reject you. If you will perform good in all your placement rounds , personal interview etc. You will get what you worth. Your aptitude, behaviour in college, with your teachers , all these things matters. Sorry no need to worry.