patch_size = dataset.shape[0] - ground_truth.shape[0] + 1

This line of code calculates the patch size by subtracting the shape of the ground_truth array from the shape of the dataset array. This assumes that the two arrays have the same number of dimensions and that the ground_truth array is a subset of the dataset array.

The resulting value is the number of elements that need to be taken from the dataset array to create a patch of the same size as the ground_truth array. This value is typically used to extract patches from the dataset array for training or testing machine learning models.