The probability that the arrow will land on any of them <em>once</em> is 1/4.
The probability that the arrow will land on any of them <em>twice</em> is 1/4 * 1/4. This is because the probability of Event A <em>and</em> Event B is P(B) * P(A).
Based on this:
1/256
Hope this helps, let me know if I missed anything!