You will be graduated at the end of the academic year (May, June or July) and you have not received your Degree yet when applying on OLAGE.
Never mind ! You can apply but:
1/ please provide a provisional certificate of graduation written by your current university right now, and upload it in the field named "highest diploma"
2/ then, as soon as you get your Diploma, upload your highest Diploma (it may be after June).
Thanks