0% offset means the projector would be level with the bottom edge of the screen. -50% offset would mean that the projector is even with the middle of the screen.
Now... I'm not POSITIVE - But I believe the super cheap, super crappy projectors on Amazon that are like $200 or less, and advertised at 5,000,000,000 lumens, are much closer to 300 lumens in the real world and if you dig in you may find their native resolution is 1280x720 or similar. Those models MAY have -50% offset. Not that there is any way in the world for you to find this information out.
For what it's worth, 100% offset would put the bottom of the screen 1 full screen height above the center of the lens. So, a screen 50" tall would find the bottom of the projected image 50" above the center of the lens... WAY up on the wall.
AAXA is likely not advertising the offset accurately.
I am working (slowly) on putting together a list of topics to cover in videos for Projector Central. Look for them to start popping up hopefully over the next few months. Offset, lens shift, and keystone correction will likely all be in this list of topics covered.
OF NOTE: Any projector with significant lens shift, like the Epson 3100, will be able to be placed anywhere from the bottom edge of the screen to the top edge of the screen or ANYWHERE between!
Depending on the actual usage and need you have, a used home theater model with a good working lamp could potentially work.
OF NOTE: This is kind of what I was thinking about as an option:https://www.ebay.com/itm/Panasonic-PT-AX200U-LCD-Projector/164031742548?epid=66715754&hash=item26310dc254:g
It has a LOT of lens shift and is a 720p model. Dated, but a decent model and fairly bright if you need a bit more screen size. Getting the shorter throw distance you want may prove very difficult.
[Edited by AV_Integrated on Jan 18, 2020 at 4:43 PM]
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