Citizen AN0 Series Instruction Manual page 17

The Chronograph 1/20 second hand will still indicate the correct time
measurement even when the chronograph is started by pressing button B while
the Chronograph 1/20 second hand is functioning as one step movement.
The Chronograph 1/20 second hand automatically stops at 00 second position 30
seconds after the chronograph is started.
When the chronograph is stopped by the button B, the Chronograph 1/20 second
hand indicates the elapsed time.
When button A is pressed again after the chronograph has been reset, the
Chronograph 1/20 second hand starts to function as one step movement to
confi rm watch operation.
* The hour/minute hands indicate the current time even when the chronograph is
being used.
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