Minimum Advance for Booking determines how far out from today’s date/time that one of your customers can schedule an order. The purpose of this setting is to give you enough time to fulfill an order. Generally, our clients do not want their customers scheduling an order on short notice (such as on the same day or the immediate next day).
Customers will receive a "Short Notice Message" for any orders placed within a 24-hour window of today's date. To modify this message or receive text alerts, please see the following article: Short Notice Text Alerts for Orders.
The default minimum time for booking is “2 days”. If today is March 10th, then the soonest available order date is March 12th. Your entry can be formatted in hours or days (i.e. "12 hours" or "3 days"). This setting is available under Admin > Order Config > Misc Order Settings: