Nomad 20 not to stated specs - Goal Zero Nomad 20 Solar Panel

I tried this out on a clear sunny day and found it couldn't even charge 6000mah past 25%. I found some tricks that it charges poorly directly facing the sun so it needs to be almost facing flat just above 30 degrees from not being hit by the sun for the best charge. Which this important difference isn't described by the company tutorials. From the design aspect the offset angle would help keep the cells from overheating however theres no way it can provide 20 watts direct 10 watts usb as described from the specs. I bought it for hiking trips but something this bulky and underperforming is going to stay home.