Your code will be 02. This is because you have already completed your 12th but are going for improving your scores. Code 02 says: The Higher/Senior Secondary Examination or the Indian School Certificate Examination which is equivalent to 10+2 Higher/Senior Secondary Examination after a period of 12 years study, the last two years of such study comprising of Physics, Chemistry, Biology/Bio-technology (which shall include practical tests in these subjects) and Mathematics or any other elective subject with English at a level not less than the core course for English as prescribed by the National Council of Educational Research and Training after introduction of the 10+2+3 educational structure as recommended by the National Committee on Education.

But if you failed in any subject and then you are re-appearing for the exams, then your code will be 01 because technically you haven't completed your 12th. Code 01 says: A candidate who is appearing in the qualifying examination, i.e., 12th Standard in 2020, whose result is awaited, may apply and appear in the test but he/she shall not be eligible for admission to the Undergraduate Medical Courses, if he/she does not pass the qualifying examination with the required pass percentage at the time of first round of Counselling.