This scanning/inspection message warns you that the X-position of some textboxes are negative.
In the above example, the selected textbox has an X-position of -5mm, which would cause the present message to be issued.
Note that this message is only issued for textboxes (ie. objects that contain tokens or text that could be Sara'ed). If you need some color to bleed off the page, then you should set the box contents to None, as shown in the above image.