What does nodulizer 3-8/5-8/7-8 refer to?

Brief introduction of nodulizer:
Nodulizer, also called rare earth magnesium ferrosilicon alloy, is an additive that can promote the crystallization of graphite in ball milled cast iron. It is generally used in the field of cast iron. In the process of casting iron, the additive added to molten iron to precipitate graphite in a spherical shape is called nodulizer. , and nodulizers containing rare earth elements are called rare earth nodulizers;
                           
Rare earth magnesium ferrosilicon alloy is mainly composed of ferrosilicon, calcium, magnesium, rare earth and other alloys through melting and configuration. It is a good nodulizer and has strong deoxidation and desulfurization effects. Magnesium is the main raw material for the production of rare earth magnesium ferrosilicon alloy;
3-8 nodulizer Nodulizer supply model: 3-8 nodulizer, 5-8 nodulizer, 7-8 nodulizer
3-8.5-8.7-8 refers to the brand name of the nodulizer, which is equivalent to the name of a person. The nodulizer can also be called rare earth magnesium ferrosilicon alloy.
Among them, 3, 5, and 7 in 3-8.5-8.7-8 represent rare earth content, while 8.8.8 in 3-8.5-8.7-8 represent magnesium content;