Russia has estimated its energy resources (oil, gas). At the same time, Britain and the United States gave their estimates. As a result of calculations, it turned out that Russia estimated its natural reserves half as much as the United States and Britain did. Why Russia understates its reserves?
Most likely, this variance resulted from the fact that Russia estimates only readily available reserves that are already in development. Because using other hard-to-reach deposits is more expensive and requires new technologies. Russia may have problems with that, partly due to sanctions.