Data Storage Overage. Data storage used in in excess of the “Storage Credit" listed in Table 3.2 (Subscription Term Fees and Credits), or in an accepted Quote, will be invoiced at the price listed on the most current Quote Client has accepted for the applicable Subscription Year. Invoicing intervals for Data Storage fees will be set at the discretion of MMI, but not more often than every three (3) months. Data storage is calculated by the space used by Client on the main production system(s) only; space used for backups is not invoiced. Due to time zone differences, data usage calculations may vary by up to three hours. Client may not carry over credit for Data Storage not used during a Subscription Year. Archive data storage used by Client (subject to availably) will be invoiced at the price listed on the most current Quote Client has accepted.