An anomaly is something that stands out relative to a comparison rule. A flag means inspect the evidence; it does not prove fraud, failure or a wrong measurement. Apply endpoints carefully and distinguish a number's value from the number of times it appears.
Worked example
A practice sensor flags readings outside 10 through 20, including both endpoints in the allowed range. 10 and 20 are allowed. 9 and 21 are flagged. A flag tells us to investigate the reading, not secretly replace it.
Invented Sensor Log
The allowed range is 10 through 20, inclusive. Six readings are 12, 15, 20, 21, 9, 15. The review team checks the instrument, units and recording before deciding whether a flagged value reflects a real change or a measurement problem. These are invented data, not health or safety readings.