The quote is wrong, the measured dose was 400 millisievert, Not 400 microsievert.
There has been a lot of flip-flopping millisievert vs microsevert, and I doubt anyone reporting it has any idea of the difference. One is measurable and a concern, but not a disaster. 400 Millisievert is a disaster. People cannot do their jobs in that level of radiation. They will begin to fell health effects after 15 minutes of exposure.
I have to condemn the Japanese authorities for not properly reporting this. Surveys are done all over the place and they know those numbers. Just report them. Report them accurately. Send them to the nuclear engineering faculty at MIT and get them to report accurately . it is not hard.