How are terrain mesh coordinates determined?

I’d like to understand how terrain mesh coordinates are determined in relation to the 0,0 world origin coordinates when “Always export at origin” is not checked in the mesh output node.

I’m trying to line up a terrain mesh with the same terrain made from a heigh map in Unreal 4 and the mesh has to be scaled up 35% for some unknown reason, and I have to drag the mesh origin way far to the right for it to line up with the terrain. I’d like to be able to calculate the scale and coordinates, instead of having to line up the mesh visually.