docs: adds example timeline for alerting for

docs/sources/alerting/rules.md

@@ -56,10 +56,8 @@ If an alert rule has a configured `For` and the query violates the configured th
 
 Typically, it's always a good idea to use this setting since its often worse to get false positive than wait a few minutes before the alert notification triggers. Looking at the `Alert list` or `Alert list panels` you will be able to see alert in pending state. 
 
-Example timeline of an alert.
-{{< imgbox max-width="80%" img="/img/docs/v54/alerting-for-dark-theme.png" caption="Alerting For" >}}
-
-In the previous image you can see how an alert rule transition over time. 
+Below you can see an example timeline of an alert using the `For` setting. At ~16:04 the alert state changes to `Pending` and after 4minutes it changes to `Alerting` which is when alert notifications are sent. Once the series falls back to normal the alert rule goes back to `OK`.
+{{< imgbox img="/img/docs/v54/alerting-for-dark-theme.png" caption="Alerting For" >}}
 
 {{< imgbox max-width="40%" img="/img/docs/v4/alerting_conditions.png" caption="Alerting Conditions" >}}