Restore anywhere drive considerations

Hi Experts,

I have a DC being backedup using SSR 2013,The C drive being backed up is allocated 120GB,wherein only 20 GB is used space .I have a backup job running successfully using SSR.I need to restore this server in my vmware environment.I tried to assign a Harddisk space of 30GB in new virtual machine and started the restore process.The recovery my computer wizard ends with invalid disk.Is there anyone here who can guide me with the minimum disk requirements for the restore process.

Thanks in advance