Scene 8 of Macbeth is a little...extended. (Sorry, Big Willy—we still love you.) There's a lot of entering and exiting and other fancy stage directions, so sometimes editors break up the scene into multiple parts.
If you see a Scene 9, 10, or 11—or a Scene 8, parts 1-4—that's why. The Big Guys (Folger, Oxford, Riverside, & co.) all do it with 8 scenes, so we're following suit.