If you are using an Auto-Trace on what I call a “Coloring Book” image, the auto trace will place a path on either side of the black line that it sees. Auto-trace routines place a path into the interface every place a color change happens.
I’ve actually got a little writeup on it here:
To avoid it, you will want to do a center-line trace on that kind of image. (Line #62 at the link below:)