Dear Abhisek,
what is your release/SP level?
Please check if note 1644463 is applicable (and do not care about the description,
it will solve an issue with this screen as well).
Afterwards, there should not be a radiobutton, but rather an additional
field 'Percentage Rate' in the installment repayment detail screen
(changed behaviour with EhP5).
Hope this helps,
Marie
SAP TRM