I had bought a square LED light panel that was advertised as 21 watt. Inside I found there was a strip of SMD LEDs type 2835, count is 90 of them. I searched and found some specs that these are .2 watts each. If so, 90 of them would seem to add up to 18 watts. How can this be considered to be a 21 watt fixture? The driver that came with it has specs: Model XJ 1518, Input AC86-265V 50/60Hz Output DC24-40v 300mA +-2% Can someone please tell me what be the actual wattage?