Using the actual points chosen: (0,05, -0.05), (-0,05, 0.05), (0,0), (0,0), (0,0), (0,0).
First to find the cluster center, I just take linear average, which is [(0,05, -0.05) + (-0,05, 0.05) + (0,0) + (0,0) + (0,0) + (0,0)]/6 = (0,0).
Because the cluster center is exactly the same as one of the points chosen, the shortest distance is 0. Then anybody not on the center scores 0/(some distance) = 0.
To use the example points A(0.4,0.9), B(-0.1,-0.5), C(0.6,0.2): The cluster center is [(0.4,0.9) + (-0.1,-0.5) + (0.6,0.2)]/3 = (0.3, 0.2).
Point A distance is sqrt[(0.4-0.3)^2+(0.9-0.2)^2] = 0.7071
Point B distance is sqrt[(-0.1-0.3)^2+(-0.5-0.2)^2] = 0.8062
Point C distance is sqrt[(0.6-0.3)^2+(0.2-0.2)^2] = 0.3
The shortest distance is 0.3, then A scores 0.3/0.7071 = 0.4243, B scores 0.3/0.8062 = 0.3721, and C scores 0.3/0.3 = 1.