Filesystem : Free Vs Available

It's mentioned as , in EXT3 disk, the available space is total free space including the reserved space for root and free space is the free space that a normal user can fill. Is that right?

Here goes my mounted volumes:
=============================
kesavan@kesavan-Ideapad-Z460:~$ mount|grep sda
/dev/sda7 on / type ext4 (rw,relatime,errors=remount-ro)
/dev/sda9 on /home type xfs (rw,relatime)
/dev/sda1 on /media/DATA type ext3 (rw,nosuid,nodev,uhelper=udisks)
/dev/sda2 on /media/11ea96ae-e372-4cd9-baa4-3f07008d0c6f type ext4 (rw,nosuid,nodev,uhelper=udisks)
/dev/sda6 on /media/bfbc93c8-62db-4b3e-9cce-a01860d098f2 type ext4 (rw,nosuid,nodev,uhelper=udisks)

And the disk-free report:
========================
kesavan@kesavan-Ideapad-Z460:~$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda7 3.8G 3.5G 92M 98% /
udev 1.5G 4.0K 1.5G 1% /dev
tmpfs 578M 992K 577M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 1.5G 144K 1.5G 1% /run/shm
/dev/sda9 7.5G 6.9G 610M 93% /home
/dev/sda1 308G 300G 0 100% /media/DATA
/dev/sda2 20G 18G 618M 97% /media/11ea96ae-e372-4cd9-baa4-3f07008d0c6f
/dev/sda6 82G 63G 15G 82% /media/bfbc93c8-62db-4b3e-9cce-a01860d098f2

No space for user:
==================
kesavan@kesavan-Ideapad-Z460:~$ date > /media/DATA/date.txt
date: write error: No space left on device

But for sudo(root):
===================
kesavan@kesavan-Ideapad-Z460:~$ sudo date > /media/DATA/date.txt
[sudo] password for kesavan:
kesavan@kesavan-Ideapad-Z460:~$ cat /media/DATA/date.txt
Sun Jul 13 09:24:13 CDT 2014

After I change the permission of file to 'chmod a+w' , user is allowed to append into the file.

kesavan@kesavan-Ideapad-Z460:~$ chmod a+w /media/DATA/date.txt
kesavan@kesavan-Ideapad-Z460:~$ date >> /media/DATA/date.txt
kesavan@kesavan-Ideapad-Z460:~$ cat /media/DATA/date.txt
Sun Jul 13 09:24:13 CDT 2014
Sun Jul 13 09:24:57 CDT 2014
kesavan@kesavan-Ideapad-Z460:~$

What is the logic behind? Is that possible to make more space for user (non-root) on reserved 5% space with help of ***tune2fs***?

Thanks,
Kesavan Muthuvel
http://kesavan.info
!!! Freedom Matters !!!