How package quality is calculated?

[OrbintSoft]

I found many topics on how package quality should be calculated by npm, but i can't find any official documentation.
I have a package with 65% of quality, 100% test coverage, but doesn't matter what I do,I am unable to increase quality.
I don't think it's good to rely on blogs, stackoverflows or other third party opinions, the algorithm can change and I think it should be publicly documented.