Committed memory part of reserved memory or not

Committed memory part of reserved memory or not

When viewing memory details of a .NET application using DebugDiag 1.2,
this is what I see -

and

Below this, this is what it is for heap 1 details -

Now, from the first two images it appears that the commiited memory and
reserved memory are different and together contribute to total virtual
memory. But from the last image it seems committed memory is a part of the
reserved memory for the heaps. Is that so ? Why such a distinction ?