Unfortunately, there is no historical reporting available for people who have visited your site before you added Pure Chat. All visitors who have interacted with your chat are stored as a contact record on the Contacts page. All chats and emails are stored in the Transcripts tab.

There is also graph on the Visitors page that will track the total amount of visitors to your site in 5 minute increments and you view your traffic numbers for the past month in that same graph.