It might be where they're measuring. He went on to indicate that at the gate, the measurements had just reached the milli- level; perhaps the exorbitantly high figure is very close to the core?
I'm pretty certain that anytime "600 to 800" was mentioned, it was supposed to be in uSv, and that those measurements were taken at the plant's gates.
Takeaway for me from this: units for radiation exposure suck, and don't communicate well to the lay.
http://www.ustream.tv/channel/nhk-world-tv
EDIT: They indeed did so, but shortened and dumbed it down with only 2 figures being provided by 'WLJG'--2.3 and 6.4 mSv 'near the plant', with the latter being the peak at the time of 'leak.'
http://www.tepco.co.jp/tepconews/index-j.html
Here are the latest ones for Fukushima-daiichi:
http://www.tepco.co.jp/cc/press/betu11_j/images/110316c.pdf
The columns are, in order, date, time, location (often 正門, the main gate), gamma rays, neutron radiation, wind direction, wind speed. The latest peak seems to be 10.85 mSv/hr at 12:30PM on the 16th, down to 2.5 mSv/hr less than one hour later.