A question about understanding the air sampling results

On March 24th you said that even at the highest levels of radiation that you had detected you'd have to breathe the air for 2000 years to equal a plane flight. But in the chart for March 24 it says for Cs 137, (3.86E+03). I don't understand what the E means. You said: "The number in parentheses is the number of years of breathing the air that would be needed for a person to receive the radiation exposure of a single round trip flight" How many years does (3.86E+03) represent? Thanks for your patience and hard work.