completely ignore those estimates, as others have stated.
Bud density, pistil coloration and trichome coloration are the three factors you want to use. You need a 30-60x magnification to resolve the trichomes properly. maybe, some fancy phone can zoom in enough now? otherwise a cheap little currency checker or jeweler's loupe is good enough.
Each factor can vary a bit per plant, so it's as much an art as a science without lab equipment.. .and even then personal preference comes into play too. what does that mean? take every suggestion as a ballpark. Almost certainly have to test out a range of ripeness to know what you like best.
When you harvest a tad early, you lose some mass, but the quality will be fine. testing potency in a lab reveals this to be true in regard to thc/thca. Since we don't have it all mapped out, what we feel may be slightly different? some say 'speedier' from early and 'sedative' with more ripening (aka more amber).