VW Jetta Dashboard warning light car with bolt on side what does this mean?

According to my 2004 Jetta owner's manual, that's the fuel filler cap indicator:

" A warning light in the instrument cluster will come on if the fuel filler cap is not properly closed.

If the warning light comes on, you should turn off the engine and close the fuel filler cap properly.

Once the cap is properly closed all the way, the warning light will go out when the ignition is turned on again and the check cycle is complete. The completion of the check cycle depends on how you drive.

If the awarning light has been on for at least 5 minutes, it will go out only when the ignition is turned off and on again."