Yeah this was my guess too, I haven’t done the maths but my guess was that $1M probably just doesn’t happen to tesselate nicely into a cube so perhaps they went

Yeah this was my guess too, I haven’t done the maths but my guess was that $1M probably just doesn’t happen to tesselate nicely into a cube so perhaps they went up to a larger, more nicely cube shaped size and there might be filler in the middle?