INTERSTATE PURCHASE RETURN - IGST CREDIT IN NEGATIVE VALUE WHERE TO SHOW IN 3B

I HAD A INTERSTATE PURCHASE RETURN IN THE MONTH OF DECEMBER 2019 DUE TO WHICH RS. 100000/- IGST CREDIT IS SHOWN AS NEGATIVE AND THERE IS NO SYSTEM OF SHOWING NEGATIVE VALUE IN GSTR3B.

AND THERE WILL BE NO INTERSTATE PURCHASE IN FUTURE.

SO WHERE TO SHOW THIS NEGATIVE ITC OF IGST IN GST3B ?.

THIS ISSUE IS NOT PROPERLY ANSWERED BY CBIC OR GST HELP DESK.