What does it mean by kernel configuration "M x N"?

I have to do experiments using NxN (where N=1000) square matrices.

I am told to create a CUDA kernel of configuration SIZE_1 x SIZE_2.

Does that mean

dim3 block_size(SIZE_1, SIZE_1);
dim3 grid_size(SIZE_2, SIZE_2);

or, does that mean

dim3 block_size(SIZE_1, SIZE_2);
dim3 grid_size((N + SIZE_1 - 1) / SIZE_1, (N + SIZE_2 - 1) / SIZE_2);

or, something else


Please, explain why.

I need to do the following experiment:

You should ask your teacher/ supervisor for clarification. My guess is that it is the block dimensions