formula to make CalMag Buffer

I need to buffer my coco coir and have all the ingredients to make CalMag, just need to know how many grams per litre for Ca and Mg. I already have some recipes but I think the buffer is highly diluted. As Ca and Mg are already in my regular feed formulas so I could end up overloading with Ca and Mg.

So is there a CalMag buffer recipe for coir? Should it be different to the CalMag supplement?