The bottle suggests 0.32oz per gallon of fuel for a +3 cetane adjustment.

It suggests 0.64 oz per gallon of fuel for a +6 cetane adjustment.
That is the silver container, unless you're up in Canada in the winter, I don't think you'll ever need the white.

Nice thing is, there is some flexibility, choose your desired cetane level and go.

I use .5 oz per gallon as my reference cause its easier to figure out how much to add from the 96oz jug, and that way I don't overfill.