Total Visitors count gets increased by two

> if total visitors count is 20 currently, if i log out it shows 22

It's ok. If you click logout link, browser doing request to http://example.com/logout page and after it redirect to http://example.com/. Visitors module add two rows: first row with visitors_url http://example.com/logout , and second row with visitors_url is http://example.com/. if total visitors count is 20 currently, if You log out it must be display 22.

> if i log out and gets incresed by 3 if i login.

Must be the same. If You login, browser doing request to http://example.com/node?destination=node and after it redirect to http://example.com/node. Visitors module add two rows and total counter must be increased by 2. Why total counter increased by 3 I don't know. You can check visitors table to check requests.

Why I need to change it? It's a valid behavior. It's not a bug.