It is  a "feature" in  VM/SP and  VM/HPO. To find  out how much  space is
actually in use,  you need a more sophisticated algorithm  which tends to
break every time you install a PUT tape (well I'm exaggerating, but maybe
twice in the life  of a VM release). LMON gets  the official figures from
CP, which can be a gross overestimate.
 
  Eric