You got it, retained sheds are just when skin is left over from the shedding period. It is only a problem if it encircles the body, such as around the tip of the tail. This can cause lack of blood flow to the area and the area can die and slough off. Eyecaps, shed encircling the middle of the body and tail tips are the main thing to look for.

A good remedy for retained sheds is to get a small shoebox-sized rubbermaid container with a lid, place about an inch of luke warm water in it, place the snake in, close the lid and then place the whole container(snake and all) in the enclosure on the warm side. Leave for an hour(sounds like baking cupcakes...) and then let the snake slither through a rough washcloth or towel. Works very well.

Hope that helps