Sometimes volunteers will forget to sign-in or sign-out. When this occurs, the system will display a screen that notifies the volunteer about forgetting to sign-out and will ask the volunteer to report their hours worked on their previous assignment.
Modify the "forgot to sign-out" screen to include your logo and message.
Do you want to limit the amount of time a volunteer can sign-out of an opportunity? The portion below is from the "Sign-In Setup Options" screen. Here you can specify the maximum amount of time that a volunteer may record their time for a single opportunity.
If your volunteer opportunities last longer than 8 hours, then you will want to set the amount of time to a longer duration. According to the settings above, the opportunity for a volunteer to record their time expires in 8 hours.