its mismatch

one of the client has filed gstr 3b for october 2017 subsequently seller has revised the existing bill due to rate difference. now there is excess credit claim of 10000 in october month.

whether it is reversed in may 2018 gstr 3b return or wait for annual return and ractified the same on annual return.
if i reversed the credit in May month gstr 3b then what effect to be given in annual return