Staring day after day at images of oil billowing from an undersea well in the Gulf of Mexico, many Americans are struggling to make sense of the numbers.

Simulated oil splatter on a BP gas station sign in Manhattan, New York.

On Monday, BP said a cap was capturing 11,000 barrels of oil a day from the well. The official government estimate of the flow rate is 12,000 to 19,000 barrels a day, which means the new device should be capturing the bulk of the oil.