I think you may have misunderstood. When it says "appliances that have a power on light when not in use" it means appliances that remain on standby and therefore may be consuming current. The saving is not in the lights themselves, which are usually LEDs, and consume minute amounts of power. An extension lead is not an appliance. The indicator in an extension lead is normally a neon. These use such a small current that we used to test them by sticking one end in the power socket, holding the other end, and touching an earth point (not that I'm recommending you try it).