Hi Aspirant,
Since there are only 30% seats available through JEE mains in Amrita University and as your percentile is 78.28, it is a bit difficult to get admission. According to the percentile, your ranking should be around 2 lakh(based on previous year analysis which may vary every year). To secure a seat of Computer Science branch, you need to get the ranking under 2 lakh and for other branches it could be under 3 lakh(All datas are based on previous years analysis).So you can aim for any of their 4 campuses.

Hope this helps.

Thank you!