are those stats with or without image recognition?
unless you have a dedicated server, chances are your host is counting image views as unique visitors as well as people going to the site..
the easy way to check it is to go to the "Pages-URL (Top 10)" section..if there are image links in that list, it isn't accurate...
please show a screen shot of the Pages-URL (Top 10) section please
cuz i might be interested