The Chick Brooder is not to be compared to an incubator that will keep exact temperature. The Brooder Heater needs to be set the first week around 38-40 Celsius and then the second week 34-36 Celsius. There is a thermostat that regulates the temperature. If it gets colder than the set temperature it turns on and heats inside the unit and vice versa. If the room is getting a sunlight during the day and the heater is on, that can make the inside temp higher and if the night is getting cooler to 60s, then the heater won’t keep up the 100s. So, as a summary you should set it based on the room temperature and shouldn’t look for an exact temperature value.