I was pretty sure that 切{き}った
meant something was cut from something else. So ケーキから一人分{ひっとりぶん}を切{き}った
would mean, "one piece was cut from the cake."
However, I came across a usage which, at least at first, doesn't seem to conform to that understanding. In my JLPT textbook, there is this graph showing the number of people in the farming industry (ignore the red line, it's just a pen mark):
One question asked which of four sentences best describes the change from the beginning to the end of the graph. This is the correct answer:
一千{いっせん}万人{まんにん}を上回{うわまわ}っていたものが、300万{まん}人{にん}を切{き}った。
My erroneous interpretation was that the sentence meant something like "There were over 10 million people, but 3 million were cut." Or, in other words, 3 million cut from 10 million leaves 7 million remaining. But the graph shows it's 3 million remaining, not 7 million, so I didn't think this was the right answer.
Instead, after checking the answers and seeing that this sentence is indeed the correct description, I'm now guessing the sentence is supposed to mean "There were over 10 million people, but it was cut down to 3 million."
However, I can't see how in this sentence 切{き}った
means "cut down to", and not "cut from".
What is it that I am not seeing in this sentence, or what am I not understanding about 切{き}る
?