Thank you for posting your concern here and welcome to TrendMicro community.
Sorry for the late response on this thread. And let me assistyou regarding this concern.
May I know what type of backup driveare you referring to? Is it an external backup drive or an internal backupdrive?
To inform you, the “File not Scanned”option is only applicable for Real-Time scan and it is used by the Antivirus tomonitor malicious files or software.
And for the Smart Scan, it scans allthe required paths that are needed to be scanned, and the Initial Smart Scan is included on the Smart Scan feature but is much comprehensive as it deletes the malware that it detects from the files that it scans on the Mac computer.