Un-spamming a comment

When moderating my comments, I accidentally selected the ‘spam’ selection buttion instead of the ‘accept’ radio button. Therefore, I have two questions:

(1): How do I ‘un spam’ the comment and change it to be accepted.

(2): How does the comments that are marked spam get recorded as spam? Is this recorded and compared per name, e-mail, or IP address within the blog software database?