As soon as a driver leaves the racing circuit, enters the pit lane, a set of timers start running and these times are presented on the TV screen.
The first pit stop graphic is this one. Pit lane time is updating continuously reflecting the time off the track. The large numeral on the right hand side denotes the race position the driver was in when he entered the pit lane. This will not update until the car has passed the pit lane exit monitor.
The second graphic is shown to viewers as soon as the car passes the pit lane exit monitor, it adds extra information in a additional bar on the graphic.
The pit lane time is the total time the car has been off the track. The stationary time is the time it has taken from the wheels stopping and moving again. In other words the time for the tyres to be changed. The large numeral is the race position that the car re-enters the race. This can not be totally relied on as it is a snap shot of where the other cars are at the moment the car on a pit stop exits the pit lane. We see the race in three sectors as shown on the TV. In reality the circuit is broken up into 16 sectors for the pit wall computers and it is this information that is reflected in the above graphic. If the car leaving the pit lane encounters a car which is already up to speed and can not match this velocity, the other car may in fact get a head and the race position will be one place less. This does not happen very often, but a 16th of a 5km (3.1miles) circuit is in excess of 300 meters (1000ft).