I downloaded the latest version today and installed together with the backend module.
My module shows that 4 visitors have been there today but when looking in the backend 6 visitors are currently at my site.
I have for a while suspected that the counter don't show all visitors. I don't have that many visitors everyday but I know that in some cases more are there than the VCNT shows. For example I had over 30 visitors at one page in one day, I know since they all did a Facebook Like on that page. that day the counter only showed 8 visitors.