Why does ClamTK not always scans the same amount of files?

The range is about 4,000 to 14,000 files in HOME folder virus scanned. What I mean 9,000 then 12,000 then 6,000 then 4,000 then 14,000 then 14,000 then 5,000 and so on

That is highly unlogical, is nondeterministic, I don't see the point why it should be a nondeterministic scan algorithm