Some confusions might be bugs

[Erhushenshou]

First, I would like to express thanks for you to open source this wonderful work! I have some confusions reading the source code here:
void UTILS::ComputeRelocation(
int P,
float* opacity_old,
float* scale_old,
int* N,
float* binoms,
int n_max,
float* opacity_new,
float* scale_new)
{
int num_blocks = (P + 255) / 256;
dim3 block(256, 1, 1);
dim3 grid(num_blocks, 1, 1);
compute_relocation<<<grid, block>>>(P, opacity_old, scale_old, N, binoms, n_max, opacity_new, scale_new);
}

P should be the number of the gaussians, what does 256 represent here? what about tiles if you set blocks to 256? And why 256? is it related to the size of the projection images？