Respected Arun Sir,
The firm has FRN but as i already mentioned that it is a proprietorship firm hence there is only one PAN i.e. PAN of proprietor. So, if i select firm and edit the PAN of proprietor in both column i.e. PAN of firm and PAN of auditor signing the balance sheet then system is throwing error and asking to enter unique PAN No.
So, FRN does not become relevant here, rather the constitution of firm matters. In the case of partnership firm, one would be able to edit two different PAN asked by the system.
other views are solicited.