So I just did a quick calculation. One liter of this toner concentrate contains 5.7g selenium and 245g liver of sulfur, with carbonate and hydroxide to adjust the pH to the target value. At the 1+24 dilution, one liter of the working solution contains 10g liver of sulfur and 0.23g selenium. This is pretty much what I guessed about Poly Toner before. I've also tried to dissolve more selenium, but it doesn't dissolve very well. What happens is that, when I dilute the concentrate to make working solution, some selenium precipitates out. If I add more sodium sulfide, more selenium will dissolve but with some other problems.
The toner I use is stronger than these values but at a significantly lower pH, taking advantage of the findings of an extensive work performed by the Image Permanence Institute of Rochester Institute of Technology. However, I find that the solution becomes less stable at a lower pH, so I use an organic compound that stabilizes the toner solution, to offset this problem. So it is more rapid in action, less smelly, more stable, with less risk of staining.