These are not ordinary colors and the manufacturer will tell you. I do not use these colors. I try to keep on my palette colors that I have tested and am sure how they work. The best approch is to begin with four colors and add one at the time. The worst mistake is have many colors in your palette and not know how they work together.
Most colors come from the kiln a shade lighter than they go in.
The colors do not always look the same after firing as they do before. The best way to know exactly what the colors will look like after firing is to make a color test. The medium one use depends a great deal on the technique one plans to use. A thin medium, or open medium usually dries slowly or never dries. This medium technique allows you to work for many hours and some times days without the worry that the paint will dry.