I have attached 2 pages of DIN EN 1563 to you with red box marking which stated clearly it is accordance to mechanical properties only.
According to DIN 1563 it deals with mechanical / physical properties, as for chemical properties, it is up to individual foundry for the chemical properties %, as long as the mechanical properties, micro structure fulfill the DIN standard. I would also like to add that our foundry has DNV, GL manufacturer approval, please be assure that it is accordingly.
As discuss over the phone, if your customer need extra clarification, I am willing to provide it.