Total support includes over $70M in other income in 2018 and 2019 which is missing the required explanation in the 990's. In other words, out of the $92M in public support, $70M is unexplained other income.
Also, Open Philanthropy pledged $30 million in 2017 ($10 per year for 2017-2019) which is considered public support since they are a public charity. However that is more than the $22 in true public support that was reported. Perhaps they didn't complete the pledge.