Assay / Purity confusion

[bash94]

Hello

So according to assay formula
Area of spl/Area of std * conc. Of std/conc. Of sample * 100%

I'm having confusion with assay & purity.
And I'm not sure if purity value of standard should be included in assay formula ( if Working standard is 95% pure then 100 mg will equal 95 mg of API) ?.
Or should I multiply standard's weight with ( assay on dried basis ) as written in Certificate of Analysis ?
Or both?

Also many things are written in COA such as sulfated ash , water/moisture content, total impurities... etc. should I deduct all of these percentages to calculate purity of material?

[Consumer Products Guy]

If your reference standard is 88% pure, and you weigh 1.00 gram of that, you're in reality weighing 0.88 grams of the material, so your standard weight of 0.88 grams would be what you use to calculate your reference's actual concentration...

[bash94]

If your reference standard is 88% pure, and you weigh 1.00 gram of that, you're in reality weighing 0.88 grams of the material, so your standard weight of 0.88 grams would be what you use to calculate your reference's actual concentration...

Alright , then what does assay of raw material corresponding to ref. standard means then ?