The 3 numbers after the distro name is: used memory, free memory and used percent(= used/(used + free)).
Scientific Linux Gnome 64bit: 286 1560 15.49 CentOS 6.4 Gnome 64bit: 281 1565 15.22 Mint 14 Xfce 64bit: 249 1596 13.50 openSUSE13 Gnome 64bit : 454 1392 24.59 openSUSE12 KDE 64bit: 404 1442 21.89
You can see Mint Xfce has smallest memory cost, while openSUSE has biggest.