Also, is this particularly good news? Using the raw numbers from the headline and the deaths from here https://www1.nyc.gov/site/doh/covid/covid-19-data.page we can make coarse fatality rate estimates. I assume population of NYC is 8,400,000.
10290 / (.212 * 8.4e6) = 0.6%
Including probable deaths (which makes the death count line up more closely with excess deaths)
15411 / (.212 * 8.4e6) = 0.9%.
So it seems consistent with a IFR of 0.5%-1%. However, this doesn't account for the lag between antibody presence and death. Also, we don't know what bias sampling from grocery stores introduces, it could affect the results in either direction. Hopefully, New York releases a paper so we can get more accurate estimates.
It's good to see a prevalence study with presumably less flaws.