I have two of those incubators. I am by no means an expert, I have only done a few hatches (one current) and have not had amazing hatch rates. Having said that, I am confident that humidity has not been a problem for me and I have not followed the numbers in the leaflet. I have found that humidity is either low (under twenty) siting around 25 or over 65, if it is around 25, I leave it be, under 20 and I add a little bit of water, I monitor the aircell size and start to increase the humidity towards lockdown as the aircells are getting larger. The humidity figures in the leaflet seem to be counter to all other opinions I have encountered.