NS Addresses do not match list from parent zone

I'm troubleshooting an issue with a site loading slow.  I ran a DNS report at dnsstuff and received:

NS addresses do not match list from parent zone. This should be addressed because queries for this domain may require an extra lookup (and more overhead) because there is no direct relationship between the NS records at the parent and the NS records at the authoritative servers. This can cause delays. The mismatched NS addresses are:

Can anybody explain what this message means or point me to a document that explains further?

DNS provider is opensrs and I checked with them and they said everything is fine and they aren't familiar w/ the dnsstuff tool.

Any help is appreciated.