Update 3 5 control boundary

3-5-control-boundary.md

@@ -20,9 +20,9 @@ You can also scroll or drag your mouse to zoom in/out or move the map area.
 
 ### Changing the layer position/area
 
-When the mouse cursor is placed on the border line map in the **Area Pane**, it displays the longitude/latitude of the cursor position in the top-right of the **Area Pane**. It also displays the start and end points of the map area or cross-section position as green dots.
+When the mouse cursor is placed on the border line map in the **Area Pane**, it displays the longitude/latitude of the cursor position in the top-right of the **Area Pane**. It also displays the start and end points of the map area or cross-section position as green dots (control handles).
 
-To change the map area or the cross-section position, place the mouse on the green dots (start and end points) of the rectangle or the cross-section position, and drag the points to the desired positions.
+To change the map area or the cross-section position, place the mouse at start and end points (control handles) of the rectangle or the cross-section position, and drag the points to the desired positions.