Message count graph

I have a question concerning the message count graph in the admin console.

It gives me a message count of 4.5 , since i just did the setup of the server and did a few email test i was wondering how did i get a 4.5 mesage count or is it 4500 messages sent for that period.

If the 4.5 = 4500 messages if that is the case, i was wondering if after I`ve intalled Zimbra (defeault setting) what is the status of the SMTP relay , is it open by default or closed.

The message relay, by default, is closed.

The message count is an average, so if your messages fell across sampling periods, it may have done some division