This page explains how applicants should name documents related to 4. Certificate of (Expected) Graduation when uploading them to their online application page.
If you have not done so, please make sure to check (4.4.) Certificate of (Expected) Graduation in the application guidelines and "How to apply" in addition to the following information.

4_Graduation_1

If you submit multiple certificates, please use a different number for each transcript (_1, _2, _3…).
Example:
4_Graduation_3

If the certificate is in other languages (not English), in addition to submit the translated (English) document using the name mentioned above, you need to submit the original (not English) document using the following name.
4_Graduation_local_1

“4_Graduation_1” should be the English translation of “4_Graduation_local_1

If applicants have completed Japanese pre-university preparatory institutions for students planning to study in Japan (Eligibility Requirement 1 C) in the application guidelines), they should also upload the certificates of completing the courses offered at the institutions using the same document name as mentioned above.

If applicants have taken an official test that shows he or she possesses the academic background equivalent or superior to that obtained from a 12-year school curriculum (Eligibility Requirement 1 D) in the application guidelines), they should upload the official certificate of the test using the same document name as mentioned above.

Please check the information about how to name other documents here.