Update azure-monitor-agent-migration-tools.md

Author: guywi-ms

articles/azure-monitor/agents/azure-monitor-agent-migration-tools.md

@@ -109,9 +109,11 @@ To install DCR Config Generator:
     ```powershell-interactive
     New-AzResourceGroupDeployment -ResourceGroupName <resource-group-name> -TemplateFile <path-to-template>
     ```
-
     ---
 
+    > [!NOTE]
+    > You can include up to 100 'counterSpecifiers' in a data collection rule. 'samplingFrequencyInSeconds' must be between 1 and 300, inclusive.
+
 1. Associate machines to your data collection rules:
 
     1. From the **Monitor** menu, select **Data Collection Rules**.