According to the GDPR, personal data is any information relating to an identified or identifiable natural person (data subject). The GDPR does not consider the volume of data records as a relevant factor for classifying personal data, but rather the nature and context of the data. The GDPR requires data controllers and processors to apply appropriate technical and organizational measures to ensure a level of security appropriate to the risk of processing personal data, taking into account factors such as the state of the art, the costs of implementation, the nature, scope, context and purposes of processing, and the risks of varying likelihood and severity for the rights and freedoms of natural persons. Therefore, the volume of data records is not a decisive attribute for classifying personal data, but rather an indicator of the potential impact of a data breach or misuse.

The other factors listed in the question are more important attributes for classifying personal data, as they relate to the identification, protection, and rights of the data subjects. The data subject category that identifies the data owner refers to the type of natural person whose personal data is processed, such as customers, employees, patients, students, etc. This factor is important for determining the purpose and legal basis of processing, as well as the data subject’s rights and expectations1. The sensitivity level of specific data elements that could identify an individual refers to the degree of harm or discrimination that could result from the disclosure or misuse of such data, such as racial or ethnic origin, political opinions, religious or philosophical beliefs, trade union membership, genetic or biometric data, health data, sex life or sexual orientation, or criminal convictions or offenses2. The GDPR imposes stricter rules and obligations for the processing of such special categories of personal data, as they pose a higher risk to the data subject’s fundamental rights and freedoms. The assignment of a confidentiality level that differentiates public or non-public information refers to the degree of access and disclosure that is permitted or required for the personal data, depending on the data subject’s consent, the legitimate interests of the data controller or processor, or the applicable laws and regulations1. The GDPR requires data controllers and processors to implement data protection by design and by default, meaning that they should only process the personal data that is necessary for the specific purpose and limit the access to those who need to know.

References:

4: 5 Types of Data Classification (With Examples) | Indeed.com

7: Special Categories of Personal Data - GDPR EU

[8]: Data Classification for GDPR Explained [Full Breakdown] - DataGrail