You won't know unless you have a suitable thermometer.
We happen to have an infrared thermometer (Fluke 62 MAX Infrared from Amazon), we used that to see what was going on when the unit could not produce enough heat to cook a meal.
When set at 400 degrees, with the lid on, it reached about 390 degrees within 8 minutes. That seemed OK, however, it could not sustain cooking temperature with food in the pan. 180 degrees was all it could do with stir-fry veggies, even left in there for 20 minutes,
answered 2 weeks, 3 days ago
Set on 400º for the cooking that fill more than 1/2 full. It is very good and fast.