Making the world better, one answer at a time. They are referring to the volume, in this case of an approximate rectangle. So say your refrigerator was 6 feet tall (inside not outside), and 3.5 ft across and 3.5 ft deep.
The Kola Superdeep Borehole on the Kola peninsula of Russia reached 12.262 kilometres (7.619 mi) and is the deepest penetration of the Earth's solid surface. The German Continental Deep Drilling Program at 9.1 kilometres (5.7 mi) has shown the earth crust to be mostly porous. Drillings as deep as 2.1 kilometres (1.3 mi) into the seafloor were achieved at DSDP / ODP / IODP Hole 504B. Because the continental crust is about 45 km thick on average, whereas oceanic crust is 6-7 km thick, deep drillings have penetrated only the upper 25-30% of both crusts.
Re: HOW DEEP INTO THE EARTH HAS THE FURTHEST PERSON EVER BEEN (MINNING) The deepest mine - at least the deepest I can find any record of - is the Western Deep Levels gold mine operated by the Anglogold company in South Africa. It's depth is 12,300 feet, or 2.33 miles. The gold ore is recovered by actual miners at this depth, so they would be the deepest anyone has been in the earth. A particular problem in deep mining is that the earth gets hotter as you dig deeper.