In general, each person teaching sets the standards. If there are empty computers, some people allow students to come in to use them. Others consider this an interruption and do not want anyone to come in during class. It's a personal preference. However, clarifying with a big sign is easiest since the reservation schedule notice is not very large.
Individual are responsible for entering their own or deleting their own entires.
When questions arise, contact the individual who scheduled the classroom. If all stations are not used, there may be an opportunity to schedule a second class or individual work or individual work simultaneously.