A contact can be associated with several lists at the same time. Thus, there will be a copy of the contact in each of these lists.
Make sure you only have one list selected at a time:
- Click on the “Lists” module
- Make sure only one list is selected (it will have a green checkmark to its left)
- If necessary, click on the square next to a list to select or deselect it
- Click on the “Save” button