Visitor Session for International, Unknown, and the United States summarize the origin of visitors in percentages of hits. Geographic location is logged in the User Domain field. How it is reported is determined by the Domains tab in the Options window. Visitors - A count of unique IPs for the period of the report, whether or not they were authenticated using domain names or cookies. Persistent cookies are defined in Cookies tab in the Options window.
Cookies give the most accurate count.
Who Visited Once - A count of visitor sessions that occurred only once throughout the log file. Once - The count of visitor sessions that appeared more than once in the log file. By default a visitor session is 30 minutes. .