He might have meant in the yellow and blue specs chart,
Rated power 300watt (line 1)
Max power 400watt (line 2)
My question is at the second line from bottom of the chart.
Sine Inverter power output AC 110/220V, 50HZ/60HZ
I wonder if it works on USA grid power then, being a UK listing I was figuring it would not. I wonder what else they have?