In what context? 6GB is the size of a file on a disk or download.
My computer can transfer files that size within minutes between disk drives or USB 3.0 Pen drives.
In terms of a Video, I've got a 6GB file, which about 30 Minutes, at 1080p30. Other times, I've seen 3 hour+ Videos at Standard Definition just reach that size.
With Auido files, again it could be a few hours to several Weeks.
As for downloads, it could be a few hours to several months depending on your connection to the internet.