Storage Full after only install Ubuntu

Those numbers reference the amount of storage your Linode is allocated by your plan, and how much of that allocation you have used for your current disks. In regards to the amount of data on those disks, and how much more free space you have, you would need to log into the Linode and from the console, run something like the following:

df -h

That will give you an overview of how much free space you have on the actual disks.