瑜伽論記 2.27

2.27

上文但云：諸地獄廣十千由旬不言竪量又各四千，是故八獄竪各四千廣十千，八獄上下重疊而住。

The text above only says: the hells are ten thousand yojanas wide, and does not say that their vertical measure is also four thousand each; therefore the eight hells are vertically four thousand each and ten thousand wide, the eight hells residing stacked vertically one upon another.