Poked around their site a little and found this, seems to answer your question? https://www.overshootday.org/content/uploads/2020/06/Earth-Overshoot-Day-2020-C

Poked around their site a little and found this, seems to answer your question? https://www.overshootday.org/content/uploads/2020/06/Earth-Overshoot-Day-2020-Calculation-Research-Report.pdf https://www.overshootday.org/content/uploads/2020/06/Earth-O...