Incorrect amount in Exchange Gain/Loss

Amounts in Purchase Invoice and Payment Entry(s) were exact earlier but now automatically in Payment Entry , it has changed. After cancelling and amending the same in Payment Entry ,when i try to reconcile Payment Entries for passing Journal Entry for Exchange Gain/Loss , the amount in Journal Entry is not coming accurately(i.e, increased by Rs. 1/12/30k etc).

Please suggest what to do.