1) There is a bug in online customer module.
The online customer module shows incorrect number of guests or members that are online.
If a person let's say a "Guest" visited 6 different pages.
The total number of "Guests" or "Members" that are being displayed are adding all the records/lines that are present in online customer modules.
Let's say there is 1 Guest online.
Now, online customer module displays all the activities of a guest or member, so if same guest or member is visiting 6 different locations/pages of the website the online Guests or members shows 6 are online. But technically it's the same person who is visiting different locations. Same with members also..if 1 member and 1 guest are visiting 10 or 15 different locations on the website, the total number of guests or members that are being displays will show a number 10 or 15 but it should display 2 not 10 or 15.
2) There is one more bug in online customer module which i posted here:
https://www.nopcommerce.com/boards/t/6929/bug-in-online-customer-module.aspx