Actually, I was asking <i>you</i> to explain, or at least give your source.

I subsequently found what I believe you are working from here: https://www1.nyc.gov/site/doh/covid/covid-19-data.page which does specify New York City (as opposed to New York State) so both the numerator and denominator refer to the same thing.

Interestingly, they appear to be using a larger denominator than your 8.5 million (NYC metro vs. NYC proper perhaps?) and get a rate of 0.175% = 175.66/100,000, eg in the "citywide total" line of https://github.com/nychealth/coronavirus-data/blob/master/by...).

But this is at least closer to your figure than I was able to get previously.