I had some bantams hatch out at about 40-50 %humidity from day one until the hatch date....I just hatched out 12 little partridge cochins and it started out at 60% and the last 3 days I took it up to 80+%...I had more eggs in the incubator, but they are fine.
usually with the humidity higher than 75% the last three days some of the chicks drown in the egg. Humidity isnt like temp. it doesnt have to be perfect and can vary greatly depending on your personal preferences.