Increased files scanned

Hello, I have a user who requested her scan run at night rather than during the day.

So I moved her from the day time scan group to a night time scan group, both groups are the same other than the time schedule for the scan to take place and the Advanced Scanning Options for the night time are set at Best Scan Performance while the daytime is set to Best Application Performance.

However we notice last night that her scan took 10 hours and 5.7 million files were scanned, the last three scans that happened during the day were 3.5 million files and took around 7 hours.

I am very confused as to why the night scan looked at more files and too longer.

Please help with any ideas

SEP 12.1.2