Milling is grinding grain and, in most communities, baking what comes of it. Folk in temperate country take something like three quarters of their calories from grain — wheat, rye and barley chiefly — and a single mill serves a manor of around twenty households. Five adults and children need roughly 36 bushels a year, so the miller is grinding on the order of 40,000 pounds annually and everyone in the settlement is waiting on him.
The craft is as much mechanism as agriculture: dressing the stones so they cut rather than crush, setting the gap so the flour is neither scorched nor coarse, keeping gearing and sluice in order. A yearly Milling Success Value test measures the variance from that baseline output — a mill run well feeds the manor with a surplus to sell, a mill run badly is short before spring.
Bread is a separate question: the loaf’s quality is a Cookery Success Value test, whoever pulls it from the oven.