Microwaves have two settings. On, and off. 40% means that it’s on for 40% of the cooking time and off for the other 60%. You’ll hear it alternate, on for 4 seconds, off for 6, or something like that.
It’s impossible to say what temperature the food will get to. It depends on the weight, volume and shape of the food, its moisture content, and the overall cooking time. The only way to check is to use a cooking thermometer.