The two numbers are equivalent to an ISBN and are used by Ernst Klett Sprachen to identify a specific product.
An NP number refers to individual digital products, such as digital editions, digital Teaching Plus or digital Learning Plus. For each NP number, a single licence is required.
A PL number refers to digital packages containing more than one digital product. For example, our allango Teaching Packages and Learning Packages. For products with a PL number, the licence is activated for all titles included.