Change is inevitable, and sometimes even the prices of domains change.
And in this process, sometimes the Registry Operator opts to 'grandfather' some domains. This fancy legal term means they will respect a previous agreement even though the new one is different.
Our platform supports ending grandfathering on either transfer (change of registrar) or delete. The Registry Operator makes this decision.
The list of names in your inventory that is grandfathered can be found here: https://registrar-console.centralnic.com/graphs/file_browser/ (the object-pricing.csv file)