Hello Matsutani,
Thank you for contacting us. Currently, there is no publicly available document specifying the size or number limits for files stored in the sandbox environment.
If you have any specific concerns or issues regarding this topic that we can assist with, please let us know. We are happy to help you regarding to more details of your case. Please note that this information may not be published in the forum.
Looking forward to hearing from you. I hope this helps.
Regards,
Yutong