Hello.
Aggregate marks means the average. Like for me, my aggregate marks are the total that i have scored in pcm english computer science and used computing above 500 as each subject maximum allotted were 100.
Add up the total marks you have scored in each of the eight semesters and divide it by the maximum total of all the semesters. Multiply this by 100. This will be your aggregate percentage.

Goodluck I hope this helps you