Because of Neebo’s placement on the wrist, the body’s core temperature can’t be measured accurately due to human physiology. What Neebo actually tries to do is to determine your child’s thermal comfort level, simply put, is your child too cold or too warm. The feature is based on scientific research connecting thermal comfort to a surface temperature oscillation on the extremities, you can read more about it here. The feature’s approximate false positive is around 20%, because the temperature of extremities can be affected by external factors: a wrist covered by the body or additional clothes making it warmer, the sun’s rays on the wrist, the physiology of the child itself (eg.: hands that are always cold) or the “chills" - a condition when the body is hot while the extremities are cold etc. All of these can cause false alerts. For this reason, you can always adjust the Reference range dependent on the current situation to prevent false alerts happening.
You may also be interested to read about potential false alerts for Heart rate (HR) and Oxygen Saturation Levels (SpO2) here.