Well, according to those guidelines, this is happening "inside" the virtual machines e.g., inside my Whonix Workstation TemplateVM. Inside my Workstation AppVM it shows ample space available. I'm just not clear why I would only have this issue with a Whonix template in Qubes.
I've only installed 1 piece of software in this template so it seemed odd. I guess I'll look elsewhere for assistance.