hi,

see most of the indian institute cgpa based grading system and you have to fill your graduation marks in most of the application either in cgpa or in percentage system. in theoretically cgpa and cpi is same and cpi is the average of the all semester spi you have obtained in your exam. however if there is option to enter for percentage then it would be better to use percentage since you have percentage of marks in your provisional certificate.  however if possible do contact with exam control authority for clarification.