When setting up Inventory Picking Rules with Shelf Life Days, how is Allocation calculated?

Inventory User Guide specifies:

Enter the shelf life days if applicable. If you enter a value in this field, then the system allocates the material the number of days that you enter in the Shelf Life Days Item Master window field before the lot expires. For example, if an item is set to expire in ten days, and you enter four days in the Shelf Life Days field, then the system allocates the material at least four days before the material expires. 

In the user guide example above, "if an item is set to expire in ten days", what is the FROM date that is used to calculate the expiration date window? Is it the Order Creation Date? Order Booked Date? Scheduled Ship Date? Pick Release Date?