THROTTLE SYNCHRONIZATION PANEL
In some AUTOTHROTTLE modes, such as ARM or THR HOLD, the pilot can control the throttle.
At the time of switching to these modes, the position of the physical throttle (HARDWARE) and the position of the throttles in the virtual cockpit (SOFTWARE) may not be synchronized, which will lead to a sudden unintentional change N1. If system detects this state, the THROTTLE SYNCHRONIZATION panel will be shown, and you should align software and hardware symbols by moving your joystick physical throttle.
After aligning, the symbols will disappear, and you will be able to control the throttle from the joystick.