System/Resource contains files that store information about resource usage and their sizes. In particular, this is where the resource size table is stored.
This resource is found in Bootup.pack.
Its canonical resource path is "System/ModelDivideTable.byml".
This resource is found in the unpacked content files.
Its canonical resource path is "System/Resource/ResourceSizeTable.product.rsizetable".
ResourceSizeTable.product.rsizetable is the file where the resource size table is stored.