I have the 3000u hanging from my ceiling so maybe I can help. Yes, that diagram is confusing and incorrect.
First, are you planning to use the automatic 16/9 <-> Scope zoom feature?
If yes, then the most you can offset the PJ is to the edge of the screen. By that i mean, if you plan to hang the PJ, and the top edge of your screen is 7' off the ground, the lens of the PJ has to be at about 7' or lower to make use of the auto zoom feature. (I will clarify, you can have more of an offset and still technically "use" the auto-zoom feature, it is just that with more offset than the top of the screen, when you zoom out to the scope setting the large offset will cause the image to shift too far down and will result in the scope image being shown on the lower part of your screen and the wall below it.)
If you do not plan to use auto zoom, you can have even more offset than just to the top of the screen. I believe you can have it as much as half of a screen height above the top edge of the screen (so the lens of the PJ would be a full screen height above the center point of the screen on your wall) but don't quote me as I'm not positive. If you trawl the huge 3000u thread I believe they covered this a few times.
Lastly, if I haven't made it confusing enough, as I said above you *can* still technically use the auto-zoom feature even if you have the PJ lens mounted above the top edge of your screen. It is just that every time you zoom in and out, you will need to manually dail in the lens offset to get the picture to raise/lower back in place to fill your screen (which kind of eliminates the "automatic" part, but adjusting vertical lens offset is still much easier and quicker than manually adjusting zoom or focus imo. So the auto-zoom feature would still have some merit.)