The Smart Thermometer's ambient temperature sensor is located within the top black ceramic housing and reads the air temperature directly around your meat. Ambient temperature readings can take some time to calculate, in which case "..." will be displayed in the app before you see a number. Your readings may also differ from the reading on your oven or grill, as those readings are either an average of the appliance or a specific location within the appliance. The Smart Thermometer shows you the temperature directly around you meat and is a better representation of your actual cooking temperature.
Ambient temperature readings can also fluctuate depending on placement, method of cooking, and the appliance you use. Most ovens heat using a wave pattern, meaning they continuously turn themselves on and off so it gets warmer and cooler in the oven causing fluctuations (example: you set the oven temperature to 400f, the oven heats up to 420f, then cools down to 380f before heating back up to 420f). While the oven continuously displays 400f, the ambient temperature reading of the Smart Thermometer may show this up and down change–which is normal and to be expected.