blocksPerGrid = (filas+threadsPerBlock-1) / threadsPerBlock => Why is this calculated?

I saw this post.

const int filas = 128;
const int columns = 128;
const int N = filas*columnas;
const int threadsPerBlock = 16;
const int blocksPerGrid = (filas+threadsPerBlock-1) / threadsPerBlock;

Why do you use ‘blocksPerGrid’ like that?
thank you.

This expression is rounding up the blocksPerGrid value, such that blocksPerGrid * threadsPerBlock is always larger or equal than the variable filas