if you have your final MBBS registration number then definitely you will feel that up but if you have not yet got the document of a final MBBS registration certificate from the health University to which you are affiliated you'll have to to fill up the provisional registration number making sure that you have the provisional registration certificate or ID xerox at the time of verification of documents for the chief examination because if you are unable to produce when you might be in a fix and your candidature might be questioned