It depends on the amount of suspended particles..
The purpose of the jar in the dark is to kill photosynthesis and the algal growth dies. If suspended particulates settle in the light-it's dirt/clay. If it only settles in the dark-it's algal in nature, or both.
Generally, in my experience if suspended clay is the issue and you have serious turbidity, the highest rate is best, like 200lbs per ac ft, just don't forget the buffer of hydrated lime if you already have fish stocked. The added benefit of 1 more negative charge the HL provides helps clear even more and keeps pH stable.
Phos takes less Alum than clay suspension does so the idea of the jar test is 2-fold...is it mechanical disturbance, is it colloidal clay (which tends to stay in suspension) or is it algal in nature.
