Magensium chloride/sulfate ratio in 2 part solution

[kaboom]

I am a little confused as to what the ratio of magnesium chloride to magnesium sulfate should be when using in combination with a two part solution additives. I've seen numbers such as 7:1 from Chemmaster and 5:3 from Bulk Reef Supply. Is there a correct ratio and why is there such a dicrepancy between the two?