Mismatch Notice

A notice has been issued u/s 73 in which it was mentioned that there is a difference of turnover but there is no difference in turnover. But actually there is a mismatch in input between 3B & 2A. The amount mentioned in the notice is cumulative mismatch amount of FY 2017-18, 18-19 & 19-20. But in the notice only one financial year was mentioned i.e. 19-20.

So Please suggest how to reply to this notice