I think the article got confused between per-week and per-day; otherwise the numbers are internally inconsistent, and difficult to believe. I don't think the top quartile of the US exercises 3 hours a day! And there's no way the bottom quartile exercises 49 minutes a day: 49 minutes a week for chores, errands, and walking to/from your car sounds more correct.

Also note that they were wearing hip pedometers, which might overestimate "moderate" exercise compared to something that also tracks heart rate.