What are the stains that might appear inside the box?
These oil-like stains are caused by the paraffin used for sealing the edges of the planks. The cardboard used for the packaging is porous and tends to absorbe some of this paraffin, which gives the box an oil-impregnated or oil-stained looking. This oil-stained looking is not a problem. It proves that the product is perfectly protected with paraffin.