The aggregate marks do not carry much importance as they are the passing marks you scored in all semesters. Don't worry about backlogs that much. Calculate your marks after clearing them.

Now, degree percentage is different at every university, and VTU will calculate your score based on your performance from 5th-8th semesters and show that on your degree. 

However, the good news is that outside VTU, you should state your overall percentage which is your actual percentage.