dear Murugan,

In the TNEA online application portal, the column name register number in both 10th and 12th standard describes entering the ROll number of yours present in the mark sheet.  the permanent registration number and roll number are not the same. As you said you have entered the permanent number instead of roll number, you have made a mistake while filling the application form. So i advise you to kindly refer to change details in the application portal and enter the roll number provided in the mark sheet.

All the best for your future.