The JAWS screen reader adds graphic or button to object descriptions when it's narrating a published course. This is how JAWS is designed to operate for accessibility support.
For example, JAWS adds graphic to descriptions of pictures, screenshots, and characters, since these elements are graphics. Similarly, JAWS adds button to descriptions of buttons and objects with click triggers.
See also WebAIM's article on Designing for Screen Reader Compatibility.
A Note About Text Boxes
JAWS also adds graphic to text box narration, which can be confusing for learners, so we added a programmatic workaround in Storyline 2 and later to suppress this behavior in JAWS.