GSTR 2A +20%

Note that we are filling GSTR 3B for the month of Oct,2019 as on 05/11/2019 . we did not know that new Input Tax Credit rule ( GSTR 2A + 20% ) was introduce from 09/10/2019 . As per our Book of Calculation Oct,2019  (Output Tax  - Input Tax) come Rs. 2,40,500.00  (As per old Calculation) which Paid & fill  Return. But if New Input Tax Credit rule follow then Our Tax Liability Come 2,85,200.00. Now what to do  because GSTR 3B return not revised.........