Guild Wars 2

Say I have a Superior Rune of the Elementalist and I have 6 on.

1) +25 power
2) +17 condition damage
3) +50 power
4) +40 condition damage
5) +90 power
6) Burning and Frozen last 20% longer.

Is the total benefit the total of each rune x 6 since I have 6 items on. That adds up to
990 power, 342 condition damage, and burning and frozen last 120% longer

or

Do you only get the benefit of each tier applied once and you need all 6 to get all tiers meaning power total is 165, condition damage total is 57, and burning and frozen last 20% longer

or

Does the highest value in the list get applied meaning the total power I get is 90, the total condition damage I get is 40, and hot/cold yada.

Having 6 runes gives you 165 power, 57 condition, 20% longer burns and freeze.

You get one bonus per rune. When you have all six runes, you add up all the bonuses on the rune.