I need to know now please help!!!!

I am having trouble with this item called Bright Powder i'm not sure exactly how it works but this is what i know, it either reduces the opponents accuracy or raises the evasiveness by one stage.

So just say i'm in a battle and i use the move Double Team 6 times my evasiveness would of reached 400% (can only use Double Team 6 times in a battle) but i also have the item Bright Powder attached would this mean that my evasiveness would reach 450% or would it reduce the opponents accuracy by one stage which would also sort of reach 450% overall.

See where i'm stuck, this might help you but it did'nt help me.

Double Team description: http://www.serebii.net/attackdex-dp/doubleteam.shtml

Bright Powder description (try to look for it): http://www.serebii.net/diamondpearl/items.shtml

Stat changes description: http://www.serebii.net/games/damage.shtml

Bright Powder raises Evasiveness , not reducing opponents accuracy
I don't get the percentage stuff though

Well thanks for that anyway.

I thought that the glare of the Bright Powder lowered the opponents accuracy

once you use double team 6 times your evasiveness would be at its fullest so the brightpower wouldnt do anything for you

but you might get fainted for using double team 6 times, and it might not help doing it without something for protection