Many LED wall controllers take a cropped section of the input signal, so that they might show a 640x360 crop of the top left of a 1280 x 720 video.
This is done to ensure 1:1 pixel mapping without scaling.
Things to ask:
1) what is the actual pixel resolution of the screen?
2) what is the dot pitch (ie pixel size)?
3) what is the allowed resolution of the video signal (this will be different from 1)
4) does the LED controller do scaling of the input signal?
5) color gamut / color profile (LEDs have brighter primary colors than you are used to, especially green)
If you get a chance, try to connect to their system and play the Resolume test card.
You can make the appropriate adjustments as a Composition level Transform, or even in Advanced Output.