How does Chaos know the size of Box Falloff?

I am not seeing box extent being passed into the field system. How does it know the actual box size?
All the field system actors seem to have boxes set to size 50. Is this the default assumed size?

A FieldSystem itself is so to speak infinit.
The CullingField tells the FieldSystem to cull everything outside the Box.
Note: The Boxes WorldTransform (Position/Rotation/Scale and therefore it’s size.) is passed.