The Copies tab of the record card shows any exact copies of the current resource. If you have multiple resources with the same ISBN they will show in this list, regardless of how you have added them.
You can use the copy feature to add more resources via the 'Add Resource Copy' feature at the bottom of the record card.
Keep in mind that when editing the information on a resource, the information on any copies will also be changed.
Be aware that if you use the 'Unlink Resource' button on the Advanced Tab to separate a resource from the others, it will no longer show in this list and cannot ever be relinked.
If you wish to export this list, you can do so by pressing the image of a USB pen. You can also tweak the view of this table by selecting the page view icon.