Subscope for row update webhook


I am trying to create a webhook that is triggered by a row update in my sheet. I would like to limit the event to a subscope of columns so that the webhook only fires when a cell in certain columns is updated.

I am using, and set up the webhook as object type: row, event type: update, and the selection of columns I want included in the subscope but upon testing it, I can't get the webhook to fire.

Am I misunderstanding how the subscope function works?

Thank you