Productivity sliders

How do these work? Take the blacksmith for example. Productivity is dependent on how many people work there, right? So these sliders, are only in relation to each other then? So 4 tools. 2 swords and 1 heavy tool or cog or what its called, would be the same as 8/4/2? But the slider goes so far so you can make 10/5/1 or what?