None- No allocation takes place.

Period- Use this method to set up a time schedule for allocating the forecast quantity. When you select this option, you use it along with the Perfield, where you specify a quantity; the Unitfield, where you select the unit of time; and the Endfield, where you specify the ending date of the forecast horizon.

Key- The forecast quantity is allocated according to the period allocation key that you specify in the Period keyfield. You can use this method when you want to take seasonal variation into account.