Forum Private forum, members showing as guests
 

I'm helping a friend with his Forum and trying to figure some things out for him hence my question.

I understand that members can show up as guests when they are at the logon page but not logged in, I get that, I also understand that they can show as multiple guests if they have visited the logon page using different browsers, maybe on different PCs (and their session cookie hasn't expired yet).

There is however something that I can't explain, when I visit the Who's Online page of the forum (4.0.3) it states 22 members and 10 guests when I'm on page 1 (with 20 members listed) and then when I go to page 2 is states 22 members and 2 guests and lists 2 members and 2 guests.

It seems to me that something is wrong here ? is this a known bug perhaps ?