Count picked items in Contentment Datalist for BlockList label

Questions
,
1

I have a Contentment Datalist where I want to count the picked items for a BlockList label.
I’ve tried the following on a property named: `people`

{people.length}

{umbValue: people.length}

But none of the above gives me anything

2

Here is how to do it:

${ people.length }