On one hand it makes no sense because "it's just a number, like 12345, how can you copyright that". But because of digital encodings, any content can be represented as a string of numbers. If we really go down that reductionist route, if numbers can't be copyrighted, then nothing could be copyrighted...

I'm ok with that, personally, but the rightsholders aren't, lol.

It also (interestingly enough, I guess) means that an online random number generator will occasionally produce illegal output because some of those numbers will translate into DMCA circumvention devices. Crazy world we live in where the law can't even catch up to the issues of 3 decades ago, much less today's.