? Didn't it say like 20 feet max?
Depth of Penetration War head designation Weapon Systems
Penetration of reinforced concrete: 1.8 m (6 ft) BLU-109 Penetrator GBU-10, GBU-15, GBU-24, GBU-27, AGM-130
Penetration of reinforced concrete: 3.4 m (11 ft) BLU-116 Advanced Unitary Penetrator (AUP) GBU-15, GBU-24, GBU-27, AGM-130
Penetration of reinforced concrete: 3.4 m (11 ft) BLU-118/B Thermobaric Warhead GBU-15, GBU-24, AGM-130
Penetration of reinforced concrete: more than 6 m (20 ft) BLU-113 Super Penetrator GBU-28, GBU-37
How many feet was it from hole to hole?
Another source:
When the bomb hits the earth, it is like a massive nail shot from a nail gun. In tests, the GBU-28 has penetrated 100 feet (30.5 meters) of earth or 20 feet (6 meters) of concrete.
http://science.howstuffworks.com/bunker-buster.htm