Clearly my HD isn't showing over 20GB of data added to it, as the DATA-DOWNLOAD folder is only showing 852mb. So what is this tracking? How does my ISP account for that number? Did I just use 20GB of bandwidth in 15 minutes?
That's the accurate number (the 852MB). And yes, Newsbin does do what they mentioned (and why you have that little program running alongside Newsbin (or some other method as I haven't fired up the program for a while now) - as it's handling the compressed headers and turning them into something the program can use for you).
And yes, pulling headers can take a serious amount of time the first time you look at anything - their retention rate is absolutely insane.
Long, long time Newsbin user here.