From the "Audit History" section of the View Account page, click a date/time combination to view the previous audit information.

A report page will display the information, and includes an "Audit Summary" that summarizes the total number of devices, manufacturers, and pages.

If there are Invalid Printer Audits, they will apear with a red font at the end of the Grid; you will be able to restore them by pressing Restore link on the first column.

If the device can't be recognised(matched) correctly, then you can't restore the invalid printer audit, so the Restore option will not be available.