Excess Output Liability paid and excess input claimed in 2018-19.

Hello,

In the Month of June 2018 and July 2018 i have by mistake paid excess output liability of Rs. 28000 and by mistake claimed Excess input of Rs. 40000.

Net effect i claimed excess input of Rs. 12000 in 2018-19 financial year.

GSTR 1 has been filed correctly for 2018-19.

The same came to my notice recently.

How can i rectify the same? March 2020 return is still pending, shall i make adjustments in march 2020 or any other way???