"other call number system" and "call number" is the same - bug or feature?

The "other call number system" and "call number" fields are linked for me. i.e., when I edit one the change is carried over to the other. Seems to work both ways. Am I missing something, Is this how it's supposed to work?

Your call number field is dependant on which possibility you have chosen for your account.

Correct, not a bug: the "Call number" field will pull/match up with whatever call number system you've chosen within your other settings (https://www.librarything.com/settings/yourbooks).

Yea, it's set to "personal or custom system", but I still don't get why there's two fields with the exact same data that I can't edit independently?

>4 Jannes: It is the same for you. If you select one of the other classification systems as your default, then they will be different.

There is more than one classification system. Each has a field. And there is one more field that shows one of them - the one you want to call your system.