[math-fun] innumeracy at JPL?

From http://www.jpl.nasa.gov/news/news.cfm?release=2011-204 : "The dust is minus 429 to minus 416 degrees Fahrenheit (about minus 221 to 213 Celsius) -- colder than Pluto, which is about minus 400 degrees Fahrenheit (204 degrees Celsius). " This is not the first time they've blown the conversion between F and C. But the last time, they used the usual conversion formula for temperatures, but applied it to a temperature difference. Can you see what they did this time? I assume they started with the article in Science, which quoted dust temperatures of 17 to 23K and slightly misconverted those numbers to Fahrenheit (for domestic readers?), then grossly misconverted the results to Celsius.