Lol, I don't know why either, maybe my watt meter is faulty, but is seems to coincide with the estimates in hwinfo (considering the power wasted from the walls to the system).
My 620w is working, but the motherboard sometimes powers off (still has lights, no post code, thermals are ok), But won't power on unless I remove some of the hdds. Lol
Not really my main reason why I wanted to upgrade my psu. I'm also planning to build an htpc/casual gaming pc off an old office pc and use my old strix gtx 970 and the 620w for it.
Thanks.