Tree Cover Prediction with Deep Learning tutorial

1

I am curently trying to follow this Tutorial and I can’t seem to understand the following sample code:

raster_value = {
   '0%': (0, [0, 0, 0, 0]),
   '10%': (1, [163, 235,  153, 255]),
   '30%': (2, [119, 195,  118, 255]),
   '50%': (3, [85, 160, 89, 255]),
   '70%': (4, [58, 130, 64, 255]),
   '90%': (5, [36, 103, 44, 255])
}