The question states that there are 5 energy contours, each with a potential difference of 0.3 J/C. The center is a conducting core, and the very outer edge is a sheath. The outer sheath is the final energy contour. Therefore, the outer edge of the center conducting core isn't an energy contour, since the question states there are five energy contours.
Consequently, I am wondering if you would still consider moving from the center core (black dot) to the very first equipotential curve to be a potential of 0.3? Would you still consider the black dot to be some potential difference than the energy contours?