Every notification has to be tied to a specific text field on the template. First select which field you will use, then include %@ in the Change message and then make a change in the Value field and a lock screen notification will be sent out.
As long as %@ is in the Change message, users will receive a notification every time Value is updated.
Including %@ in the message prints the content of the Value field in the notification. You can also add any text around it in the Change message for more context. Just avoid using % in the change message since that can cause issues for iOS users where the notification text would be replaced by a generic one.