Merge pull request #213330 from AbbyMSFT/metric-alerts

Set Aggregation granularity greater than frequency to avoid missing first eval window

Author: prmerger-automator[bot]

articles/azure-monitor/alerts/alerts-create-new-alert-rule.md

@@ -90,8 +90,8 @@ And then defining these elements for the resulting alert actions using:
         |Threshold value|If you selected a **static** threshold, enter the threshold value for the condition logic. |
         |Unit|If the selected metric signal supports different units,such as bytes, KB, MB, and GB, and if you selected a **static** threshold, enter the unit for the condition logic.|
         |Threshold sensitivity| If you selected a **dynamic** threshold, enter the sensitivity level. The sensitivity level affects the amount of deviation from the metric series pattern is required to trigger an alert. |
-        |Aggregation granularity| Select the interval over which data points are grouped using the aggregation type function.|
-        |Frequency of evaluation|Select the frequency on how often the alert rule should be run. Selecting frequency smaller than granularity of data points grouping will result in sliding window evaluation.  |
+        |Aggregation granularity| Select the interval that is used to group the data points using the aggregation type function. Choose an **Aggregation granularity** (Period) that's greater than the **Frequency of evaluation** to reduce the likelihood of missing the first evaluation period of an added time series.|
+        |Frequency of evaluation|Select how often the alert rule is be run. Select a frequency that is smaller than the aggregation granularity to generate a sliding window for the evaluation.|
 
     1. Select **Done**.
     ### [Log alert](#tab/log)