Browsing Time is calculated by looking at the date/time stamp of each hit, and then grouping the hits into sessions. Whether a hit falls into a particular session or not is based on a special 'threshold time'. The default threshold time in WebSpy Vantage is 5 minutes, but you can change this in Tools | Options| General.
If two hits are written to the log file within five minutes of each other, they are grouped into the same session. If another hit is made within five minutes of the second hit, this too is added to the same session. If there is a break of more than five minutes with no hits made, then the previous session is finished and a new session is started when the next hit is made.
The total time of one session is calculated as the time between the first and last hits of the session. The time of all sessions is added together to get the total browsing time for a user.
If a user browses to a website and then walks away from their computer for an hour, no time will be added to that user's browsing time while they are away from their PC. Only the initial 2 seconds to open the website and download the resources will be added to their browsing time. Note: Time may be added to their Browsing Time if the website they have opened has self-refreshing banner ads or tickers.