Understanding Closest Pair Algorithm (CLRS)

Question

I'm reading CLRS Section 33.4 Finding the closest pair of points. At exercise 33.4-2 they say

33.4-2

Show that it actually suffices to check only the points in the 5 array positions following each point in the array Y'

But I'm getting 4 array positions following each point in the array Y' will be suffice to check. See the fig below

Which possibility I'm missing. Can anybody point it out.

Answer 1

Assume that a point exists in every corner in the figure (including the inside corners). If points cannot overlap, then you have 6 points that can reside in the 𝛿x2𝛿 box, and since you must be looking at one of them, you need only compare it to the next 5 in Y'.