I don't get this comment, are you joking? 0.8 micrograms per cubic meter "isn't great"?

Typical concentrations of pm2.5 in outside air in winter time where I live are roughly 200-250 micrograms during the day, and into high hundreds (400-800) to thousands (highest I've seen is 3000) in the evening.

Yes, this is correctly measured by multiple sources.

This is what "isn't great" looks like, not your less than 20% of the latest WHO recommendation.

Unless it's just a mixup/typo.