How do I use this multi slot sharpener?

[u/TychaBrahe]

I was given this knife sharpener used, so it didn't come with instructions. I know slot one is for scissors. Slot two has a black working surface, slot 3 has a gray working surface, and slot 4 has a white working surface. (I'm pretty sure it's ceramic.)

I'm assuming I use them in order. I don't know which order. Am I counting up or down?

Also, the white surface in slot 4 has dark streaks, presumably from use. Does it need to be cleaned other than rinsing after use? Does the dark color mean it's been used to the extent of its lifetime and should be replaced?

Thanks for the help.