This is the pseudocode on how the labelling in PC1 works. It's for the 32GiB sector size production parameters.
node: A "node" refers to a 256-bit (32 bytes) value of the padded input data. A 32 GiB sector as 1m nodes.
label: A "label" refers to a 256-bit (32 bytes) value of one of the layers. It's the result of hashing the node index, layer index, replica ID and multiple labels together.
parent_file: That's a pre-generated file (it's fixed and the same for everyone) that contains a list of random 32-bit integers that are used as offsets to read from a file.
padded_data: A 32GiB file that has the padding already applied. "Padding" in this case means that each 0th and 1st bit is zero. It could be validated as: