The chart showed the increase over time:
However, looking through the comments, I came across this comment from Scrvpvlvs: "Your fine article prompted me to compare the two browsers’ growth rates", dated the same day, under his blog post: "Chrome Heats Up Faster Than Firefox".
And in three charts he makes the data totally meaningful. The original poster quoted some figures from another website and stated that Firefox had five times more users than Chrome - implying that we should see the 70 million in that context.
Scrvpvlvs' charts show that these are indeed impressive figures because it shows the growth of Chrome. first by market share over time: