Anything around 50-60% is adequate, for most hatching, with a bump in the last three days.
I have rarely been able to maintain textbook humidities and I have hatched a LOT of chicks.
The fact that you actually have a hygrometer and are monitoring humidities is a wonderful thing.
It's been my experience that you'll do much better at hatching if you understand Rh and then select good eggs from vigorous stock.
Technology is not the end-all answer to successful hatching, much as we like to think so. That is actually the easy part. This is evidenced by those who make functional incubators out of cardboard boxes and electric skillets and use no hygrometers.
Breed stock that is purposefully developed to produce strong, vigorous chicks is much more important, IMHO, than techno wizardry - and harder to come by.
I can only sudder when I hear about people who simply can't bear to cull, keep their yards overloaded with a watered down menagerie of stock and have no plan for the breeding that goes on in their flock.
Like the tuffold hen says, as far as humidity goes you sound fine.