Difference in amount by genius & rules

Hi all, 

I filled return of an employee who recieved arrears for year 2013-14, 2014-15 & 2015-16 altogether in year 2016-17. Genius software shows relief of Rs. 11400/- for him in payable tax under section 89 but when I calculate manually the amount is Rs. 16300/-. I checked many times but unable to find the difference in these to figures for same data. Is Genius software giving wrong result ? I appreciate all help. Thanks.