Hello aspirant!!!

You need to enter the optional subject as computer science/computer application/ biology. Its based on your group which you had chosen in your 12th grade. It is not important to mention your subject name. That mark is not taken for your counceling.

For more details about tnea counseling refer to the following link below...

https://www.google.com/amp/s/engineering.careers360.com/articles/tnea/amp

All the best!!!

Stay safe!!!