The official bulletin states that only those Candidate's whose Caste falls under Central OBC list should select their Category as OBC and the rest should fill in their Category as "General Category." Now if your Caste isnt listed in Central OBC list, then you should have selected General Category. Now because you selected OBC, unfortunately it is a wrong entry. You cannot take admission under General Category because NBE doesnt allow any changes once the correction window has been closed.