That would make it a major spill (more than 100,000 gallons), and a heckuva lot more than the 4 gallons in total that was reported to the National Response Center. But not unexpected if the Anglo-Suisse well the Coast Guard has pegged as the source was actually leaking for three days (rather than 4-6 hours), as this news report suggested:
The spill was first reported to the NRC at about 8pm on Friday, March 18, three full days before the Louisiana officials came across the continuing effort to plug this well.
Wildlife and Fisheries officials found the source of the oil Monday evening and encountered workers in a boat trying to restore a cap on the well using a remotely operated submarine.
"Well-capping went out of control," the state official said.