If they're giving it to you in nitrate-nitrogen units then 8.414 mg/L is 37.256 nitrate mg/L. API uses nitrate units. Not sure about Seachem.
As far as I can tell, the tests report just nitrate, as they suggest the ug/L limit is 10,000, which fits in the standard EPA nitrate (not nitrogen-nitrate) limit.
However, the explanation you've given me for nitrate-nitrogen levels seems to fit the numbers I'm looking at from various test kits (API strips and liquid tests, and the Seachem test kit).
I have to admit the colors from 40ppm - 80ppm on the various test kits are hard for me to distinguish, but none of the tests suggest anything near 8.414 ppm.
The company I use for well water testing is certified for the results they produce in our state, so I'm apt to trust them. But perhaps it's better to trust, yet verify, by having another lab to nitrate alone tests.
Is 40ppm nitrate baseline in an aquarium cause for concern?
Bump: Actually I take that back, the EPA suggest that 10,000 ug/L is the limit for nitrate measured as nitrogen. So am I looking at nitrate-nitrogen numbers? And is my nitrate level in terms of aquarium test kits closer to 40 ppm?