A problem whit Tracked files daily hits

I have a problem with tracked files. In the "Daily Tracked File Access" graphic shown in the summary, i can see the number of hits/day every file received, but when i enter a single file detail the Daily Activity table show me 0 hits per day . Even strager ...the General Statistics show me p.e. a total of 12 hits for this file but a 0 hits/day average. Important: I know all this hits come from spiders but i have checked the "count spiders as visitors' option. Is it a bug or I'm doing it wrong ?