Hi, you will need to change the volume size as suggested by JGPSHNTAP to display the units in GB. From the Data ONTAP 8.2 Commands: Manual Page Reference For 7-Mode, Volume 1...
When displaying the flexible volume’s size, the units used have the same form as when creating the volume or setting the volume size. The specific unit chosen for a given size is based on matching the volume size to an exact number of a specific unit. k is used if no larger units match.
However, these are very large root volume sizes. Are you storing a large number of logs? It is normally recommended to only store system files in the root volume. Would a dedicated syslog volume help in your situation? Or do you have a large number of dump/crash files that could be cleared out?
Just for info...the recommended (min) root volume size for the larger controllers is only 250GB + 5% snap reserve, please see Hardware Universe for exact recommended size for your system.