Well with each round you play in chaos you get to vote on the type of mini-game.
Each map with give you a % chaos, and some other item. like +8 trap ..
The % chaos is what you are aiming for or higher (what ever the achievement requires)
the % after all rounds (before vat defense) needs to total 150%.
Round 1 = 15%
Round 2 = 50%
Round 3 = 35%.
Round 4 = 25%
Round 5 = 35%
vat protect = 0% (always)
total will be 160% thus gaining you the achievement as long as you complete the vat round successfully.
Of course with the mini-game being voted on, you find that some groups will automatically pick a game they find easier or a lower percentage of chaos.
I've personally had 148% because the group i played with picked a 35% over a 50%.
Also the very first round is picked automatically, you will get chaos for it, but you wont know if you hit over the 150% till the the vat protection time. So again, each round you actually get to pick make sure you aim for the highest amount of chaos as possible.