Where's my MegaBytes?

Before installing a variety of packages associated with the H. Dip. in Web Technologies course, I noticed something strange about the operating system image that I had written to the newly acquired 8GB SD Card; my megabytes had disappeared! The size output below should add up to close to 8GB rather than somewhere less than 2GB!

pi@raspberrypi:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
tmpfs                  94M     0   94M   0% /lib/init/rw
udev                   10M  168K  9.9M   2% /dev
tmpfs                  94M     0   94M   0% /dev/shm
rootfs                1.6G  1.2G  300M  80% /
/dev/mmcblk0p1         75M   28M   47M  37% /boot

Following this excellent step-by-step tutorial, I was able to 'recover' the lost space on the SD card.

The root (/) has 5.6GB space available giving me more than enough space to install Ruby on Rails, Apache, MySQL, and space to learn to develop web applications.

pi@raspberrypi:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mmcblk0p2        7.3G  1.3G  5.6G  19% /
tmpfs                  94M     0   94M   0% /lib/init/rw
udev                   10M  164K  9.9M   2% /dev
tmpfs                  94M     0   94M   0% /dev/shm
/dev/mmcblk0p1         75M   28M   47M  37% /boot