Their actual values were 86.83 years, 86.52 and 85.94 years. Oglala Lakota County had a life expectancy of 66.81. Lo and behold, 86.83 - 66.81 is more than 20 years.
From the source article:
> Counties were combined as needed to create stable units of analysis over the period 1980 to 2014, reducing the number of areas analyzed from 3142 to 3110. In 2014, life expectancy at birth for both sexes combined was 79.1 (95% uncertainty interval [UI], 79.0-79.1) years overall, but differed by 20.1 (95% UI, 19.1-21.3) years between the counties with the lowest and highest life expectancy.
Pretty cool data viz here: https://vizhub.healthdata.org/subnational/usa