deemed income tax amt

1. According to sec 115JC which deals with AMT was introduced was non-corporate taxpayers who are claiming deductions under
i) Chapter VI-A sec 80H to sec RRB (except sec 80P) (or)
ii) Deductions u/s 35AD  (or)
iii) Sec 10AA profit linked deductions for SEZ units. 
Only person who claims any of the above deductions AMT provisions will be applicable. 
2. For assessee's who are claiming unfair deductions or misusing the above deduction provisions of AMT was introduced. 
3. In computing AMT items of deductions claimed are only added back to arrive at Adjusted Total Income and 18.5% was applied on the same. 
4. In your case, you have mentioned the AMT income figures in negative. Make sure you have entered all the cells correctly and there is the column where you have mistakenly entered any amount. Because AMT will only increase your total income and it cannot decrease your income. And there is no ITR-3a and it might be ITR-3 if I am not wrong. 
Please correct me if the above interpretation has an alternative view.