Yes, the values are rendered on top of each face with "pixel" maps (ascii art) that have the character of the digit they represent as each pixel. These are later manipulated by the perspective projection.
For example on this d6 you can see the top face has 1s written down (in the shape of a sideways one) and the front one has 4s written down in the shape of a skewed and sideways 4.

In this specific color scheme there's not a lot of contrast between the values, but even in the palettes with better contrast, good readability is something I'm kind of giving up on solving well.
edit: might be clearer here:
