Docs Fleet add section about RollingUpdate fields

RollingUpdate is not working when replicas number is updated.

site/content/en/docs/Guides/fleet-updates.md

@@ -26,12 +26,21 @@ much of the `Fleet` is  incremented and decremented at one time:
       maxUnavailable: 25%
 ```
 
-So when a Fleet is edited, either through `kubectl` `edit`/`apply` or via the Kubernetes API, this performs the following operations:
+So when a Fleet is edited (any field other than `replicas`, see note below), either through `kubectl` `edit`/`apply` or via the Kubernetes API, this performs the following operations:
 
 1. Adds the `maxSurge` number of `GameServers` to the Fleet.
 1. Shutdown the `maxUnavailable` number of `GameServers` in the Fleet, skipping `Allocated` `GameServers`.
 1. Repeat above steps until all the previous `GameServer` configurations have been `Shutdown` and deleted.
 
+{{< alert title="Note" color="info">}}
+When fleet update contains changes of `replicas` parameter, than new gameservers would be created/deleted straight away,
+which means in that case `maxSurge` and `maxUnavailable` steps parameters will not be used.
+
+For the case when you want to be flexible on Fleet size, Fleetautoscaler and a Fleet config with omitted `replicas` parameter should be used.
+
+[Read Fleetautoscaler guide]({{< relref "../Getting Started/create-fleetautoscaler.md#7-change-autoscaling-parameters" >}}) for more details.
+{{< /alert >}}
+
 ## Recreate Strategy
 
 This is an optimal `Fleet` update strategy if you want to replace all `GameServers` that are not `Allocated`