Q: Strange mark left by unplugged MagSafe Charger

Hopefully someone here can explain this. I had my charger unplugged and sitting next to my computer. It hasn't been plugged in in over 12 hours. When I moved it to plug it in, I noticed that there was a discolored reflection of the charger imprinted on my table - almost like a radiation shadow or x-ray. The strangest part for me is that, because the cable is spooled, the charger isn't resting flat on the table. This means that there is no chance that the charger (which is clean) somehow had ink or something that was transferred to the table. Sorry if this is confusing but I've never seen anything like this before and want to make sure that my charger is safe for use. Thanks.