diff --git a/src/ApiManagement/ApiManagement.ServiceManagement/Commands/NewAzureApiManagementSubscription.cs b/src/ApiManagement/ApiManagement.ServiceManagement/Commands/NewAzureApiManagementSubscription.cs
index a9aec2cecb14..7cfa777ec6ef 100644
--- a/src/ApiManagement/ApiManagement.ServiceManagement/Commands/NewAzureApiManagementSubscription.cs
+++ b/src/ApiManagement/ApiManagement.ServiceManagement/Commands/NewAzureApiManagementSubscription.cs
@@ -80,14 +80,14 @@ public class NewAzureApiManagementSubscription : AzureApiManagementCmdletBase
             ValueFromPipelineByPropertyName = true,
             Mandatory = false,
             HelpMessage = "Subscription primary key. This parameter is optional. If not specified will be generated automatically." +
-                          " Must be 1 to 300 characters long.")]
+                          " Must be 1 to 256 characters long.")]
         public String PrimaryKey { get; set; }
 
         [Parameter(
             ValueFromPipelineByPropertyName = true,
             Mandatory = false,
             HelpMessage = "Subscription secondary key. This parameter is optional. If not specified will be generated automatically." +
-                          " Must be 1 to 300 characters long.")]
+                          " Must be 1 to 256 characters long.")]
         public String SecondaryKey { get; set; }
 
         [Parameter(
diff --git a/src/ApiManagement/ApiManagement/help/New-AzApiManagementSubscription.md b/src/ApiManagement/ApiManagement/help/New-AzApiManagementSubscription.md
index b0cf9ae2ba42..d75d35dad2a6 100644
--- a/src/ApiManagement/ApiManagement/help/New-AzApiManagementSubscription.md
+++ b/src/ApiManagement/ApiManagement/help/New-AzApiManagementSubscription.md
@@ -117,7 +117,7 @@ Accept wildcard characters: False
 ### -PrimaryKey
 Specifies the subscription primary key.
 If this parameter is not specified the key is generated automatically.
-This parameter must be 1 to 300 characters long.
+This parameter must be 1 to 256 characters long.
 
 ```yaml
 Type: System.String
@@ -164,7 +164,7 @@ Accept wildcard characters: False
 ### -SecondaryKey
 Specifies the subscription secondary key.
 This parameter is generated automatically if it is not specified.
-This parameter must be 1 to 300 characters long.
+This parameter must be 1 to 256 characters long.
 
 ```yaml
 Type: System.String