If you entered into a customer agreement on or after March 2, 2021, you are subject to the Overage Billing Policy, in which event the terms of the Overage Billing Policy govern.
For a single backup job of a client on the primary CFA, the protected space will be larger than the used cloud storage on the secondary (cloud) CFA. Once versioning comes into play (scheduled backups are running), this will change, and the used cloud storage will be larger than the protected space.
For the Backup & Disaster Recovery–Cloud, the Fair Use Policy allows for the fair use limit—that is, the used cloud storage can be as much as 3 (three) times the purchased cloud storage.
For the Backup & Disaster Recovery–Local, the Fair Use Policy allows for the fair use limit—that is, the used cloud storage to be as much as 2 (two) times the purchased cloud storage.
Once the Fair Use limit is nearly reached or is reached, you have the option to either reduce the used cloud storage by using the retention policy to remove some versions, or to increase your purchased cloud storage so it is greater than or equal to $^1/3$ ($^1/_2$ for Backup & Disaster Recovery–_Local) of the used cloud storage.