The only way to have an image in there more than once is if you put it there. Maybe you had a reason for doing this?
If Movie Studio works the same way Vegas Pro does, change the view in your Project Media tab to "Details" and look in the "Use" column.
If you click on it, it will sort from low to high or high to low.
Anything with "2" or more is probably a duplicate event.
In the screenshot below, there are a number of instances of various events and this is because it was a few long ones that were split up as needed.
