600w MH Conversion

This has me a bit dumbfound, so I suppose I will get some suggestions.
running a 600w MH conversion on a switchable ballast. (magnetic)

being as 600w MH are conversion only(as far as I know) and meant to run on a straight HPS ballast, what is the purpose of the MH option?

which setting should I run my ballast on?

What? What is it you want to do? If HPS then run the HPS side of the toggle switch. If MH then . . . .. It has to do with starting each.

updated the first post. was a bit tired when i posted. seems the question would be straight forward if you actually understand anything about growing equipment.

but i added the needed info to the first post i guess.