When you delete a row with a Card, you are only removing the Card from the List, not deleting the Card.
Delete an individual row
Right-click anywhere on a row to see the action menu. Select "Delete Row".
Delete multiple rows
Select the rows you want to delete. The bulk action menu will open on the right-hand side. To "Select All", click the double tick on the bulk action menu.
Note, to deselect all Cards, click the X at the top of the bulk action menu.
Click the icon at the bottom of the bulk action menu to remove your selection of Cards from the List.