Do not worry too much. Even though it would be ideal to both write the name of the degree and the name of the subject, writing the subject code is enough for purposes of review. In most universities and examination boards, the use of subject codes determines specific courses and assigns them to proper examiners.

Here's what you can do:

Contact Your University: Call the examination department or your course coordinator. Try to explain the situation and see what further steps need to be undertaken.

Check Your University's Guidelines: Just check out your university's guidelines for examinations or check with your course instructor; most probably, they will be able to give you the precise information on how such discrepancies are handled.

Trust the evaluation process: Most universities have provisions for resolving such minor errors. The examiners should be in a position to determine the right subject based on the subject code and the content of your answers.

In any case, be calm and try to avoid unnecessary stress. If there is an issue, the proper authorities at your university should be consulted with.

It depends on the university rules as well as examiner mostly chances are it may not get cancelled because its not a big issue if you write subject code and the answers you have given in the subject will be known by that.

sometimes this error will be corrected by the invigilators before submission of the answer sheets to the Centre Superintendent. Your result will depend on your answers that you have written.

Best wishes..