How to prevent Historical rate defaulting to prior period historical amount instead of average rate.

Historical rates table defaults to prior period historical amount in subsequent months that was entered in prior month rather than pull the current period average rate in subsequent periods.

GL: Owners Equity Translation Rule profile is set to PTD at the site level but when one month historical credit amount is updated , the subsequent months also pick up the credit amount as default instead of the Average rate.

Is this intended functionality ? How can we prevent subsequent months from defaulting to credit amount and rate type as "historic" ?