External vs. Internal exposure

I watch environmental radiation levels in Tokyo everyday. Its value barely shows external exposure level. By contrast, internal exposure is difficult to know how much one person could be exposed. It depends on air, food, water, wearing a mask or not, etc, etc.

TEPCO announced one female employee had exposed more than guideline. She was working at heavily protected building at Fukushima nuclear plant. Her external exposure is 0.78 mSv. Her internal exposure is 6.71 mSv. She overrun her limit, 5 mSv per three months. She cared for workers without mask, so she is said to inhale radioactive materials which were stuck on the clothing of workers.
http://www.tepco.co.jp/en/press/corp-com/release/11050105-e.html
http://jp.reuters.com/article/jp_quake/idJP2011050101000232  (Japanese)

It was a brief news, I don't know detail yet. but it is saying as if the place where one person is exposed 0.78 mSv as external exposure can expose the person 6.71 mSv as internal exposure.

Almost 9 times?
A total of external and internal exposure is almost 10 times of only external values?
It looks too horrible. Am i thinking stupid thing as usual ?????
I don't understand what I should learn form this news.