Those are just SCS numbers. The CNBC article cites all of CMU. Facebook recruits from the math, engineering (EE), and info systems programs as well.
2016 - 1 total from math and engineering
https://www.cmu.edu/career/documents/2016_one_pagers/cit/ece...
https://www.cmu.edu/career/documents/2016_one_pagers/mcs/mat...
2018 - 4 total from math and engineering
https://www.cmu.edu/career/documents/2018_one_pagers/cit/ECE...
https://www.cmu.edu/career/documents/2018_one_pagers/mcs/1-P...
If you're curious to do some more research, here's the link https://www.cmu.edu/career/about-us/salaries_and_destination...