Update Set-UnifiedGroup.md

Correct instance of -ExtensionCustomAttribute with a number on the end.

Author: robinmalik

exchange/exchange-ps/exchange/Set-UnifiedGroup.md

@@ -680,7 +680,7 @@ Accept wildcard characters: False
 ```
 
 ### -ExtensionCustomAttribute1
-This parameter specifies a value for the ExtensionCustomAttribute5 property on the recipient. You can use this property to store custom information about the recipient, and to identify the recipient in filters. You can specify up to 1300 values separated by commas.
+This parameter specifies a value for the ExtensionCustomAttribute1 property on the recipient. You can use this property to store custom information about the recipient, and to identify the recipient in filters. You can specify up to 1300 values separated by commas.
 
 To enter multiple values that overwrite any existing entries, use the following syntax: \<value1\>,\<value2\>,...\<valueN\>. If the values contain spaces or otherwise require quotation marks, you need to use the following syntax: "\<value1\>","\<value2\>",..."\<valueN\>".