i asmbb counts online users wrong. when refresh page it counts again same user.
I am not very sure what you mean, but yes, asmbb counts the online users generally wrong. Mainly because in the HTTP protocol there is not such thing as "online users". So, AsmBB simply counts the web browsers that have made requests in the last 5 minutes. In addition, it tries to separate the guests from the logged-in users and there can be some source of error as well.
It is fundamental problem, that can be solved only to some extent. But IMHO, this is not important at all. Think about these numbers as an approximation.