Jim,
There is no such unit as the macron, unless Emmanuel Macron decided to name one after himself. At 5'10", those would be some very large particles.
If .3 micron is real, that's about 80,000 grit which is indeed pretty fine.
For reference, here are the prefixes used in the metric system:
prefixes.JPG
Patiently waiting for some yoctometer sized polishing compound. Perhaps Stewart has a source?