Hi!

If this is in reference to the filling of application form in some university, then first of all keep your original marksheet ready so that no error is possible later on.

Contact the concerned authorities of the institute via the email id that they must have provided. Explain the problem to them and ask if correction in form is possible in any way.

Once they suggest some way to rectify the error, please follow it and fill your form stepwise correctly.

Hope it helps!