How Does Greenmangaming cashback work?

I'm planning of getting Bioshock infinite and DMC there because well, they have a 25% pre-purchase voucher and a cashback option

Now my question is, how to does cashback works

Do i need to pay (60 + 50)*(1 - 0.25) = 82.5$ first then after a few days, GMG will return 9$ on my CC? (Just like paypal putting a 1$ check on your CC)

Or 82.5$ - 7$ - 2$ = 73.5$ will be immediately charged on my CC?