That's total time spent on social media. According to the source, Facebook's usage is 38 minutes a day. I suppose this also counts people who don't use Facebook though.
https://www.broadbandsearch.net/blog/average-daily-time-on-s... puts it at 58 minutes, and https://www.nytimes.com/2016/05/06/business/facebook-bends-t... (from 2016) notes that it's 50 minutes (apparently reporting by FB in an earnings report).