Please cite the article. Humidity is a tool which is used to ensure that your air cells are the right size by hatch day. A lot depends on the egg. If it's large, small, porous or not. It also depends on how big the air cells were when they went into the incubator. Humidity levels are not "cut and dried". If I'm incubating during the winter months (up until April) I may run my humidity at 30 - 40%. Later in the season, I may need to actually run completely dry towards the end of my incubation period, and may run dry right up until first internal pip if the weather has been particularly humid. The level of humidity I run depends entirely on what my air cells are looking like. If you have not yet read all of "hatching eggs 101" in the learning center, it is an excellent compilation of science based articles and advice.
Thankyou Lazy Gardner. I have skimed that site, but not completely closed because my hatch rate had been 99% -100%. But at a much higher humidity. Now I realize that it was summer, not winter as now. I will re read that. Thankyou.