Code Markup Tool Documentation

Is there any documentation on the code markup tool?  I've searched and not found any.

I have found out that if I want to have a double line break, I need to input at least one space on the blank line.

Now I am trying to figure out indention.  I indent with spaces.  It shows up with correct indention on the Code Markup Tool's page's preview, but not in the actual post.

Thank you.