The Order Interval field represents the minimum number of days between orders.
If the Order Interval on an item is set, when that item is added to a Purchase Transaction a warning message is displayed if the item has already been ordered within the specified number of days.
The message displays the item's last ordered date, its Order Inverval value, the date at which it may be ordered again, and prompts to remove the line item
from the Purchase Transaction.
See:
Inventory Database - Order Data Screen Fields