In DPL3 (versions older than 4.0.0), namespaces with spaces in their name (such as "Help talk") requires replacing the space with an underscore — e.g. "Help_talk". If you use a space instead, inclusions and exclusions won't work as expected, and pages like Help talk:Three are not included/excluded. This is due to MediaWiki namespaces internally using underscores.
This is not an issue in DPL4 4.0.0 and later, where spaces in namespace names are handled correctly.
Code
{{#dpl:|category = Number examples
|namespace = Talk¦Help talk
}}