A world with code 0 is 0% to 5% surface water in liquid or solid form If the world is shortsleeve...
If the poles are shirtsleeve, the water will be mostly past 45°N/S. It's going to make the tropics lethally hot.
If the tropics are shirtsleeve, the poles will capture almost all the ice and there will be almost no water elsewhere.
If the mid-lattitudes are shirtsleeve, the poles are still going to trap the water mostly as ice.
That said up to about 25% (the highest allowed before becoming Hydro 3)... is likely to be merely uncomfortable...
There's also the issue of thermoregulation effect of large bodies of water. Low hydro is going to mean much wider temp swings than similar position and atmosphere. And those will migrate water towards ice caps.
Long term stable oxygen levels cannot be explained by geological processes with expectable abundances at surface of anything big enough to not get size S... conveniently, that's also right about the minimum self-rounding size...
Which is why I said imported or residual life - all life known requires water to evolve in. We'll see if Venus changes that.
Also, most people never experience true 0% humidity - there are few places on earth that actually hit that. One's lungs, however, need some, and if it isn't in the air, it comes from the blood. Fairbanks in the winter is problematic even in warm but un-humidified buildings. And that's got a local hydro of (usually) 9... but that's a thin shell of ice with almost no moisture in the air. (During the summer, it's hot and humid... but still desert.)
