why is qml editor display's top corner not coordinate (0,0)

I started from an empty Qt Quick application.
I dropped a rectangle and tried to anchor it to the window. (as a background)
Since I can't or don't know how to change its color (right click does not
bring up a color chooser, and adding the "color" attribute is invalid
I dropped a second rectangle and tied it to the top of the first rectangle
and 35 pixels in height (as a title area).
I dropped a text area and anchored it to the title element.
I did all of the positioning using the qml text editor.

Ran the build process. All looked just as I expected. Closed the app.
looked at the qml representation in the designer plug in.
I showed that the top of the designer canvas iis off the screen.
When I pull down the screen to see the top, the geo coordinates
for the background are different than (0,0).
I have included two screen snapshots. One contains the
actual running application. The second contains a snapshot
of what the qml designer shows me when I switch to it
with coordinate (0,0). I can drag down the image, but then
the background is no longer at (0,0). This tells me that
the designers (0,0) is outside of the viewing image.