Understanding Closest Pair Algorithm (CLRS)

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.