Dexcom G5 User Manual page 289

For example, if you set your High Glucose Alert to 200 mg/dL, how often will
your Alarm alert you if your BG goes at or above 200 mg/dL? In the Software
505 Adult Study (Table 6-A), when your blood sugar goes above 200 mg/dL,
you can expect your Alarm to sound 98% of the time and not to sound
approximately 2% of time within the 15 minute period before or after your
blood sugar goes above 200 mg/dL.
289
Dexcom G5 Mobile System User Guide
Technical Information