Full System Scan showing weird results

I have a simple question. I did 3 full system scans today. How come the first finished scanning around 1 million files while the other 2 finished at 500,000? No threats found but I'm still paranoid.

I did click on a suspicious website/news article today that was blocked by my browser. (Showed the red warning screen.) I pasted the link in the Norton link inspector, VirusTotal, Scanurl. and other link inspectors. Nortion is untested while the other websites say its 'probably safe'. Nothing has been downloaded but maybe this has something to do with the weird scan results? Also, not most the tech savvy. Sorry.

Don't browse the internet while sleep deprived.

After you get new virus definitions from LiveUpdate a full system scan will scan all files. During that scan, many files will be marked as safe. If you subsequently run a full system scan before new definition files are updated, those safe files do not get scanned again. When a new definition file is downloaded, all files will get scanned again.