I guess you’re sure it ran 30 minutes. But your Allowed Depletion of 50%, root depth of 9.8" and Available Water of 0.17" (I’m psychic - it isn’t shown above) results in watering each time an amount of 0.84" (0.17 x 9.8 x 0.50). Perhaps the chart is showing what it WILL water, or WOULD water?
