That appears to be space on disk for transcripts of all the traffic. Presumably if people were not uploading GB of crap, it would not need to archive GB of crap.

Unless it keeps as many copies of everything as people who get it. That would be dumb.

But I was told that is what Gmail does. Every GIF animation, cat video, and corrupted SPAM jpg attached is stored as many millions of times as people who saw it, and probably as many again as forwarded it.