It indicates the car speed.
See also:
How to use the gears
Press the clutch fully before shifting the gear stick into one of the positions
shown in the diagram in fig. 2 (the diagram is also on the gear lever knob).
IMPORTANT
Only engage the reverse gear ...
Front passenger's airbag deactivated
(amber)
Warning light comes on when front
passenger’s air bag is deactivated.
With front passenger’s air bag on, turning the ignition key to MAR, warning light
comes on steadily for about 4 s ...
With toggle lens
Press the short side of the lens fig.
91 to switch the light on and off.
...