Take the appropriate action and verify that the warning light turns off.

Taking Action
Message Indicated on DisplayMazda 6 Owners Manual: Cruise Control (Some models)
With cruise control, you can set and automatically maintain any speed of more
than about 25 km/h (16 mph).
WARNING
Do not use the cruise control under the following conditions: Using
the cruise control under the following conditions is dangerous and could result
in loss of vehicle control.
...
Mazda 6 Owners Manual: To Increase Cruising Speed
Follow either of these procedures.
To increase speed using cruise control switch
Press the RESUME/ switch and hold
it. Your vehicle will accelerate. Release the switch at the desired speed.
Press the RESUME/ switch and release
it immediately to adjust the preset speed. Multiple operations wil ...