Which site is it that your api call refers to? Seems likely that you only have 2 hostnames set on it 
The call you are making is to fetch site settings, which probably doesn’t have a 1:1 mapping with the DNS Zone you mention seeing in our UI. If you want to make the call that shows your DNS records, try finding the call we use. It may not be directly supported in the client you’re using right now since we don’t necessarily support all possible calls there, and so you may have to make it directly (which is fine with us, may be harder for you, but not against the rules :)), after you find it using this methodology: