Thank you for the question.
The subscriber information definition is based on international standards and all the work that has gone on in the international community to describe these things. Proposed paragraphs (a), (b) and (c) are supposed to cover the types of information that will be of use to police. That's why they are described the way they are with the examples after. It's to try to make them future-proof in terms of what other types of information.... For example, there's information that may be used to identify the subject and then it gives a list of examples, identifiers assigned by the service provider with a list of examples, etc. The idea is to try to be as comprehensive as possible.