This isn't exactly a bug, but it is overly challenging. The Economy production quests seem to be net rather than gross. For example, if you have resources going to science, then that lumber doesn't count. Well, for stone and lumber, I can reset the research to zero to get them to count. The real problem is the food. It will not count the food going towards population and army. I don't have an overly large population yet, but every time I upgrade the resource sources (forest, garden, etc), it adds yet more population. Trying to get enough food to register for 250 is requiring quite high gardens, and I'm only on my first few days of my new town. I fear I'll hit a point where I'll never be able to complete the quest.