Displays in the following cases:

Stop Vehicle in Safe Place Immediately
Message Indicated in Multi-information DisplayMazda 6 Owners Manual: Manual Transaxle Shift Pattern
The shift pattern of the transaxle is conventional, as shown.
Depress the clutch pedal all the way down while shifting; then release it slowly.
Your vehicle is equipped with a device to prevent shifting to R (reverse) by mistake. Push the shift lever downward and shift to R.
...
Mazda 6 Owners Manual: Instrument cluster repair
Note
The needle of speedometer or tachometer may continue to rotate
clockwise until it indicates over maximum graduation. If a customer
complains of this concern, repair the needle position according to the
following steps.
1. Verify the concern.
2. Turn the ignition switch to LOC ...