If you are wondering how much feed they actually need, chickens on average eat a quarter pound a day, so a flock of 9 needs approximately 2.25 lbs of feed available daily.
How much water they go through can vary with weather, climate/humidity, whether or not they are laying or growing etc. Generally speaking 5 quarts will water a flock of 10 for a day, so a gallon waterer would take care of your flock of 9.
With these numbers, especially with the water, I'd err on the side of providing more, not less.