Disk Usage Analyzer counts up the amount of space in use by all the files. Something like
df asks the filesystem how much space is in use. These two amounts can be very different depending on e.g. how many deleted, but still open, files are on the filesystem.
e.g. if you do something like this:
$ dd if=/dev/zero of=largefile bs=1M count=1024
$ python -c 'import time; x = open("largefile'); time.sleep(600)' &
$ rm largefile
You will see that the 1GB of space is still shown by
df, but not by
Disk Usage Analyzer. This is because while the file is still open, it is not actually removed from disk. When the python script finishes, the filesystem will free up the space.
I'm not sure if the above explains your 4.4G to 9G discrepancy, though!