Update source/adminguide/autoscale_with_virtual_router.rst

Co-authored-by: Wei Zhou <weizhou@apache.org>

Author: shwstppr

source/adminguide/autoscale_with_virtual_router.rst

@@ -183,7 +183,8 @@ Specify the following:
    it will be trimmed to fit within the limit. The limits are:
 
    - **Windows templates:** 15 characters (NetBIOS limit). The hostname follows the format `as-WinVM-<6 random letters>`.
-   - **Other OS templates:** 63 characters.
+   - **Other OS templates:** 63 characters. Unsupported characters may be normalized
+        (for example, lower-cased or replaced) to comply with OS constraints.
 
    Unsupported characters may be normalized (for example, lower-cased or
    replaced) to comply with OS constraints.