Right... Let me do what I do, I guess.
Okay, so subtracting all of the air we have a volume of stone dust that is 5.80203e14 m^3 large, with a density of 1602 kg / m^3.
That "stone dust" must have come from the ground within the sealed area. The stone beneath the Juubi has a density of 2515 kg/m^3 (from the same source Arc7 used for the stone dust density), so comparing that to the volume of dust, we get a volume of stone that is: 3.6957694e+14 m^3
The surface area of the sealed square (if Arc7's pixelscaling is correct) is 6783.66113585 m * 6783.66113585 m = 46018058.406 m^2
Dividing the volume of destroyed stone by that, and we get a depth of destruction that is: 3.6957694e+14 m^3 / 46018058.406 m^2 = 8031.12849 km
In order for this calc to be correct, the ground within the sealed area with the Juubi in it would have had to become 8031 km deeper for this amount of "stone dust" to be propelled from the sealed space. Since this is the not the case, the calc is incorrect or at the very least flawed in its assumptions.