I was just reading threw the "Book of the Skull" rules when I was given a surprise by the "Turning the dial section."

TURNING THE DIAL - When an opposing character takes damage from a friendly character equipped with a Hammer, roll a D6 and turn the Book of the Skull dial that many times to the right. If the opposing character was KO'd by that damage, turn the Book of the Skull dial 3 additional clicks. When the dial is clicked past its red line, click it one more time.

Now, I know that with "Event Dials" once a Red Line appears you stop clicking the dial. Same goes with the "Wild Dials." So in this instance, the Stop line, is not a stop line at all? Or is this a mistake on designs part as we (players) already have an understand about what the red lines do?

In the case the red line doesn't do anything other than trigger the above effect of the dial, resulting in one additional click. There's no definition within the rules for red lines to mean anything specific in terms of combat.

Also Book of the Skull is a resource not an Event Dial.

As I had said, their is a reference to what Red Lines do from a pre-existing mechanic.

The Event Dial text you quoted has nothing to do with Book of the Skull or any other non-Event dial.

The SkullBook's rules tell you exactly what to do with its red line.

And that only applies to event dials. There's no blanked definition of red lines.

This reference pertains just to characters but it illustrates that red lines don't necessarily mean stop. For a resource, or another non-character mechanic that may use a red line, look to the description of the red line to see how it is handled. It is a case by case basis kind of thing.

In the Book of the Skull's case the red line is handled by adding an extra click on to however many clicks you were going to click the dial. You know this because it tells you so. If something has a red line it will either be its red point value's starting line or the description will tell you how to handle it.

Also relevant: