2011 NEC 600 Volts & under . 314.28 A (2). 6 x 4 =24 + 8 = 32 inch by 32 inch. Depth see 314.28 A (2) exception . That refers you to 312.6 (A). 70-175. Wire per terminal 3. 600-700 wire per terminal = 12 inch Depth.
As Said by others . that is Minimum size! If you ever pulled 600 mcm you would NOT use minimum size.