The interior lights are scheduled to "fade" after you shut the door. The way the system is set up, they don't give power when you open the door and then fade them out gradually - they have 12 V to both sides of the bulb and drop one side to zero when you open the door - slowly bringing the voltage back up on the backside to 12 V when they "fade". In the regular bulbs, this reults in no lights when both sides are "hot", and lights up when the computer drops the voltage on the backside and slowly raises the voltage later.
In the case where you still see some dim light well after the doors have been closed, this is simply a matter of the voltage not coming completely back to 12V on both sides - there is a slight differential voltage to make the LED's active. I learned all of this with a volt meter, when I was trying to get my LED's on my Windrestrictor hooked up to my courtesy lights (with a diode to isolate). My Windrestrictor would not operate with the courtesy lights, so I had to install a relay - which does not like the fade part of the courtesy lights.
Long answer to a short question - but that is how these lights operate and the LED's will still stay "on", if they have more than 0.7 V of differential in the proper direction (small light - 12 V for full light). This is why they tell you to install them in one way only - they won't work in the opposite direction. Hope this helps...
