Relief under sec 89(1)

tarun kumar (any) (146 Points)

25 July 2020  
Mr. A has been received arrears in Fy 19-20 for a/y 17-18.
But in a/y 17-18 he showed full salary in ITR .
So now to take relief in Form 10E what is the calculation for p/y 17-18.
Mr. A has gross income is 550000 in a/y 17-18 out of which 250000 is arrears. And ₹275000 deduction for the same.
pls help ASAP