The bottles vary depending on what size and type of bottles. If the tray on your scale is big enough, just dump the contents and weigh out the powder. If you don't have a tray large enough just get a sturdy piece of cardboard or something and place it on the tray, zero it out, then pour the powder on the center of the cardboard. Just make sure the cardboard is not touching anything, as this will throw off your measurement.
I'm sure it weighs out correctly if you got it from 1fast...