As you have 526/600 that is 87.6 percentage in 12th Tamil Nadu Board. Now c alculate the NATA score - your board percentage is 87.6 and your nata score is 132.So nata score should be divided by 2 so your score 132/2 = 66

66+87.6= 153.6

153.6/2= 78.8 Now your final merit score is 76.8

Now you can check previous year data for various college according to your category.

All the best