Update customize-default-site-design.md

added comment about web template ID values for the modern templates.

Author: seansquires

docs/declarative-customization/customize-default-site-design.md

@@ -1,4 +1,4 @@
----
+ ---
 title: Customize default site designs on SharePoint
 description: Customize the default site designs in either the SharePoint team site or communications site template
 ms.date: 12/18/2017
@@ -13,7 +13,9 @@ SharePoint contains several site designs already available in the SharePoint Onl
 
 ## Apply a site design to the default site designs
 
-To customize the default site designs, apply a new one with the Powershell **Add-SPOSiteDesign** cmdlet, or the **CreateSiteDesign** REST API. Specify the **IsDefault** switch to apply the site design as default.
+To customize the default site designs, apply a new one with the Powershell **Add-SPOSiteDesign** cmdlet, or the **CreateSiteDesign** REST API. Specify the **IsDefault** switch to apply the site design as default. 
+
+The WebTemplate ID for a Group-connected team site is 64; for a communication site it is 68.
 
 The following example shows how to use the **IsDefault** switch to apply the Contoso company theme to the default site designs. The site script referenced by ID contains the JSON script to apply the correct theme.