hI,
Here are the specs I'm confused with
Rated Current: 22 amps
Rated Voltage: 24
Wattage: 400
It doesn't come out right
22*24=528 not 400
Am I overlooking something?
Yes. The page says "Output: 400 Watts", while you're calculating the input power.
Which means that it has an efficiency of 75.8% (given that the info is correct).