Second (as is clear from source article but, once more): via https://twitter.com/JanetCoats/status/265925450696642561
@fivethirtyeight did not account for 20% of NYT traffic; 20% of visitors to NYT looked at 538. Big difference, my math-challenged friends.
Mashable, in this instance, is just rushed and plainly false blog-spam. According to them, FiveThirtyEight "accounted for 20% of all visits to the New York Times website," probably implying page views. The original article says 20% of visitors to the New York Times website also visited the FiveThirtyEight blog.