Terrain.SetNeighbours - what is left, top, right, bottom in world space? -x, +z, etc.???

Hello community

I've never really seen this answered anywhere and it certainly isn't answered in the Unity docs. I have a script I've written which I'm popping on each of my terrains to stitch them together (they already have right heights set this purely LOD matching).

What I can't work out is what the "left", "top", "right" and "bottom" variables of Terrain.SetNeighbors() correspond to in Unity's world space. My assumption is "-x", "+z", "+x" and "-z" but lets, face it - Unity terrain can be very unintuitive, especially going from terrain coords to world so some kind of definitive information on this would be great!

Cheers

Num_T