Hello, 

As you know that the maximum marks are 400, 200 marks are considerer fron NATA and the other 200 belong to the board marks. To know your marks, you should divide your NATA score by 2 and add it to your board percentage. 

If your board percentage is 80, and your nata score is 160; add up 80 and 160/2 = 80. Your score would be 160. 

Hope this helped you 

Thank you and keep asking :)