Help me set the Plugboard to push Subtitles to my Kobo

I've created a Column in Calibre with the lookup name "#subtitle", type "Created from other columns". It has entries like "106,262 words, 6-7 hours".

I went to the KoboTouchExtended plugin, checked on Metadata:Subtitle, and tried to set the template. So now, every book on my Kobo has an entry that looks like this:
I've tried futzing with the Template Editor and the Template Tester, and I can't find a way to get the Subtitle field's data to populate to the Kobo. What should I fill in to make this work?