The same numbers appear in a Psychology Today article,
https://www.psychologytoday.com/blog...ddicts-relapse, apparently based on this study:
An eight-year perspective on the relationship between the duration of abstinence and other aspects of recovery. - PubMed - NCBI
This is apparently based on 1200 people who entered treatment, so it's among people who have a serious enough problem to go to rehab.