That means that you consistently had ~6MB/sec, or 50Mb/sec of upload bandwidth. That might be possible if you're on a really good 100Mb connection (or 1Gb connection), but that's not common in most of the world yet.
Also, could it be that the "re-upload" was able to detect your older copy of the files and reuse them? I can rsync terabytes in minutes over slow connections when the other side already has the files ...
What kind of internet connection are you on? I recently reinstalled my mac from scratch (El Capitan upgrade went haywire) and had to redo my backblaze backup. I uploaded the 500 GB to Backblaze in under 24 hours.