I built a Steamwork (yay!). But whenever I turn it on, there's nothing surplus in any of my production lines (and a consume in Coal). So, what's this supposed to do?
The Question from your Title: The Magneto Boost Ratio boost the boost of the Magneto. The Magneto boost the Global Production by 2% per building and a Steamwork boosts this effect by 15%.
But the Steamwork can more!
With different Upgrade it can produce things like Manuscript. A Full list is here