In some industries, there are documents where position data has another level. There are documents with 2-stage position data, e.g. in the case of textiles or clothing where an article (number, description) can also have a “sub-level” with sizes or color specifications. The article itself is just listed once and in the level below there are then the quantities/prices of the individual characteristics.
PDFmdx is also able to recognize and read two-stage position data, the following video shows how to do it: