So... I got 35,7 thousand cubic meters.
First thing I did... circulated entire pile volume and then selected LOWEST POINT.
Got a volume of 58096 cubic meters
I also drew two lines, to get top height and lower height along the slope. Also, to know the lines lenght.
So I took a screenshot and took it to Sketchup. I imported the screenshot and using the lines as base, I re-scaled the image until the lines were the same lenght as in DroneDeploy.
Now I circulated the exact same path around the pile as in DroneDeploy. Saved the shape for later.
Remade a simple shape terrain with the heights I got from the sloped lines at Drone Deploy.
The shape I saved later... put it above the 3D simple shape of the terrain. Draped it, Deleted the borders.
Ended up with a volume that is quite similar to the extra volume I got in Drone Deploy when using the lowest point.
USed Tig's Volume Calculator plugin, for irregular 3D volumes.
22.382 cubic meters. Subtracted it from the 58096 cubic meters.