ComputeShaders strange behavior [I'm a noob]

Unity Engine
1

#pragma kernel CSMain

shared RWStructuredBuffer _TheBuffer;

[numthreads(8,8,1)]
void CSMain (uint3 id : SV_DispatchThreadID)
{
_TheBuffer[(id.y * 8) + id.x] = (id.y * 8) + id.x;
}

public class ExecTestCS : MonoBehaviour {

    public ComputeShader CS;
    private ComputeBuffer CB;

    void Start () {
        CB = new ComputeBuffer(2048, sizeof(float));
    }
   
    void Update () {

        CS.SetBuffer(0, "_TheBuffer", CB);
       
        CS.Dispatch(0, 1, 1, 1); 
        int[] x = new int[2048];
        CB.GetData(x);
    }
}

The question:

CS.Dispatch(0, 1, 1, 1); //fills 64 positions (as I was expecting)
CS.Dispatch(0, 2, 1, 1); //fills 72 positions (i dont get it)
CS.Dispatch(0, 2, 2, 1); //fills 136 positions (now i’m lost)

2

I know i could try to guess what is happening.
CS.Dispatch(0, 1, 2, 1); //fills 128

I thought i got it, but 128+8 = 136.

3

Aside the errors of the code. I might need to internalize this https://i-msdn.sec.s-msft.com/dynimg/IC520438.png