Different number of files being scanned after separate scams

Hello, I ran a virus scan and found a few viruses on my computer about a week ago. I decided to factory reset my computer since it was fairly new and I wanted to be super safe. Since then, I have been running virus scans whenever I leave just so I can check everything and after one scan it came back with no viruses and 300k files scanned and I did another one a few hours later and it only had 75k files scanned.

I was curious what the reason for this was. Any help is appreciated!