Purchase Extra Storage.. which then expires.

A website has 500MB of storage space.

The website owner purchases 300MB of space for 12 months using 10 credits.

What happens at the end of 12 months? Does the user and/or admin get a notification asking them to renew? Can the website be configured to automatically renew? If they choose not to renew, does the available space revert back to 500MB and do the extra files get deleted?

Please explain the process clearly.

Edit: ** This thread is related to the Upgrades (https://premium.wpmudev.org/project/upgrades) plugin, I had incorrectly placed it in the Supporters plugin category.