1: Adjust your pledge and reward to the 4-pack $80.
2: Add a pledge of $23 per game for the 5th, and additional copies. For example, I live in the US and I want 6 games: $80 + (2 x $23) = $126 total (Don't forget $10 per game for shipping outside the US).
3: Contact me to confirm what you're expecting to get for your pledge: firstname.lastname@example.org
Don't see the answer to your question? Ask the project creator directly.