The Mayans used vigesimal base 20. We use decimal base 10 because we count on ten fingers, the Mayans no doubt also counted on their toes as well as their fingers. I don't think there is anything incredible about them using a different base. 3-fingered green aliens would presumably use base 6, unless they had 3 arms, then it would be base 9. Probably, more useful if we used hexadecimal base 16.
A fractal is a geometric shaped pattern that on closer examination is made up of smaller parts that are reduced-size copies of the whole. A mathematical fractal is based on an equation that undergoes iteration, a form of feedback based on recursion. Computers can be used to produce geometric fractals based upon mathematical equations that are mathematical fractals, but geometric fractals occur frequently in nature - in plant leaves and tree branches, in coastlines, snowflakes, crystals, blood vessels, river networks, mountain ranges, ocean waves, and lightening. So again, I see nothing incredible about the Mayans recognising this.