Grid Sample for Even Number?

Let say that I want to apply grid sample to a tensor. If the tensor is a odd sized number like [1x5], and we didnt want it to change, it would be [-1, 0.5, 0, 0.5, 1].

But what if it is an even sized number. I know the ends have to be -1 and 1, but what about the middle?

Is it [-1, 0.5, 0, 1] or is it [-1, 0.25, 0.25, 1] or something else?