Hello Aspirant,

CBSE 12th exam is administered by the school in the school Physics, Chemistry, and Biology labs for Science students or any other labs only. Here external examiner supervises the exam along with the subject teacher of the respective subject. So, if you have done some mistakes in writing the roll number the subject might correct the mistake as they know your name. I don't think it will lead to cancelling your paper as your last two digits are correct. It will be an inconvenience to the teacher. They won't take such drastic steps as cancelling your paper. Make sure you commit this mistake again in any exam as roll number is a vital part of an exam. Making a mistake in the roll number in the written Board exam may have a negative impact. So, just double-check your details before submitting the paper.

Regards.