Hey!

I guess you are referring to the UG NEET exam which was conducted today since you haven't mentioned the exam name as such. To answer your question, if you have shaded two circles in the same question, it won't be in any case marked as correct. It will be incorrect and will either be marked as zero or will get negative marking.

Hello,
If you have done this in one of the answers , then your answer will be marked wrong and you will lose your score over there. Don't worry , your answer sheer won't get rejected. Its just that, your answer will be considered wrong even if one of the bubbles is correctly marked.

However if you have done this mistake in filling your roll number or any other important details then the OMR machine will read it wrong. The authorities may check manually,  otherwise the paper would be rejected.
Please click the link given below for related information about OMR sheet
https://medicine.careers360.com/articles/neet-omr-sheet
Hope it helps.