In includes/functions.php around line 5415 (in function contruct_style_options) there's a line
Code:
$stylesetlist .= construct_style_options($style['styleid'], $depthmark . '--', false, $quickchooser);
you probably want to take out the
. '--'
I don't understand the code, but it kind of looks like a minor bug where they didn't fully implement the ability to change the $depthmark