Cloudwatch Anomaly Detection

The Anomoly Detection feature of Alarms is tied to standard deviations. For example a standard deviation of 1 would mean variations in price for that service would not alarm if the deviations fall within what is seen 68% of the time for that customer. If the deviation's magnitude is greater than what is typically seen 68% of the time then it will trigger the alarm.

A standard deviation of 2 will only trigger if the deviation is greater than what has historically been seen 98% of the time, with a standard deviation of 3 being equivalent to 99.7% of the time.

https://en.wikipedia.org/wiki/68%E2%80%9395%E2%80%9399.7_rule#:~:text=For%20an%20approximately%20normal%20data,deviations%20account%20for%20about%2099.7%25.

These values will vary by customer and service. If a customer/service has lots of variation of high magnitude then the bands will be wider (similarly if you choose a higher standard deviation value). If the customer/service has low amounts of deviation then, or a smaller standard deviation value selected, then the bands will be narrower.