Excise correction in er1

we are mfg. exciseable unit we filled ER 1 monthly basis. in Nov15 we filled ER 1 our range officer found in amount mismatch in at the time check. By our side assable value 260000 insted of 26000 we have duty paid correctly so what can i do with solve the issue and any correction in ER 1 of any under rule we have correct the query with range department. office ask we have issue notice. we are any letter submit before notice or any procedure with out side