The box in the upper-left corner of the Plot Properties + Plot Components tabbed dialog shows one of the expressions or functions that you are plotting in the current view. These expressions are referred to as ``items'' and are listed by Item Number. You can view the current functions or expressions by clicking the up-down arrow buttons. To change the curves or surfaces that are plotted, you can change, delete, or add expressions or functions in the box. To change an item, edit it in the box. To add an item, click the Add Item button, and then type the item in the empty box that comes up. To delete an item from the list, click the arrow buttons until the item is displayed in the box, and then click the Delete Item button.