I'm adding dynamic content to the body of an http request.
The body is json formatted.
When I add the data manually it works fine. However when I add dynamic content it get's a malformed error.
The problem seems to be a number that I'm retrieving from a sharepoint list. In the return output it appears as a green number (no quotation marks).
Code:

Output:

Can anyone help?
I've tried writing the above json to a string using Set Variable - this worked. But I'd really like to understand why the green number format is not working.
Thanks