Clustered Shots vs DR / hardness

[chaoskin]

UC wrote:

Clustered Shots (Combat)

Prerequisites: Point-Blank Shot, Precise Shot, base
attack bonus +6.
Benefit: When you use a full-attack action to make
multiple ranged weapon attacks against the same
opponent, total the damage from all hits before applying
that opponent’s damage reduction.

when i read this do i ignore all DR and hardness or i have to pass the DR or hardness before it counts (like if DR or hardness of 10 i need to do 10 point with one arrow or all arrow have to pass 10 even if i roll crappy)

[Jeff Merola]

First, Clustered Shots does nothing against Hardness. It only works against DR. Second, you add up all of the damage before DR for all of your shots, then apply DR to that total once.