The Performance Graphic legend indicates how many seats are available for sale. However, as seats selected by another operator or by a person using the web interface to purchase a ticket online are still technically available as the tickets have not yet been sold, they cannot be re-selected by another person, otherwise double-bookings could occur. Such selected seats are not in the Held or Reserved state, they are Available but cannot be selected. To inform the operator how many Availableseats are already currently selected, the legend shows a negative number after the total number of seats Avail. This number represents the number of selected seats. In the Performance Graphic’s seating layout, seats selected by other operators or users are indicated by an @ symbol replacing the letter on the seat. 

Below, six seats have been selected by another operator and are marked @. An additional four seats have been selected by this operator. Next to Avail in the legend, it says that 456 seats are available, (-10) currently selected. These ten selected seats are the sum of the six selected by other operators, and the four selected here.