Lets say you are not able to do deliveries at a certain time each day. You can set business hour to accept or deny jobs based on wether the job is scheduled in the available business hours
You can set the business hour by going to the create page and click the 3 circle button. There you will see the option to set Business hour settings
Then you will a dialog will show up where you can make the business hours
This is the type of error a user will see when they enter a time that is not the business hours