During Charlies flashback when he hears himself on the radio
The guy in the car is messing with the car CD-Radio player & we can hear the radio playing.
He is turning the dial and we see the number on the screen change from 27 to 23 and it sounds like he is searching for a channel
(we hear the radio station tuning change)
Then the guy press's the blue D button 
Stereo player is a Jensen CD3610 CD/radio player
First he Is adjusting the volume thats why the Display changes from 27 - 23
Then he presses the "D"(Display) button.
(we see the display change)
He is not tuning the radio however the Audio during this shot tells that he is tuning the Radio.