Resource limits are a powerful way to automate work in your settlement.
You can set a resource limit and then mark a recipe for continuous production or place work: your people will keep collecting or producing that resource until the limit is reached.
When resources are consumed, and the amounts fall below the limit again, your people will go back to work.
You can set any limit to 3 types of values;
Infinity: There is no limit to production; it will continue as long as there are materials available.
Fixed Amount: Sets a limit defined by a specific number of units. Production stops once the number of units of that particular resource reaches the value.
Population Percentage: Sets a limit defined by a percentage of the current population. Setting a percentage limit is useful to avoid having to adjust the limits as the population changes constantly.
Note that limits only affect work areas and automatic crafting; the limit is ignored if you explicitly give an order.