Understanding MSI directory structure

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C++

Hi,

I am reading microsoft documentation for Windows Installer. I am reading the topic "An Installation Example", in which i got an example specifying directory structure as given below

Directory	        Directory_Parent	DefaultDir

TARGETDIR		                        SourceDir
ProgramFilesFolder	TARGETDIR	        .

.................
.................
end of table

Now as far as I understood is that TARGETDIR is location where application will be
installed and it can be changed during installation using a User Interface. And the ProgramFilesFolder is a property that points to program files folder of the system.
But what does it mean by TARGETDIR is the parent of ProgramFilesFolder property? That entry makes the directory structure illogical.

Please, guide me in this confusion.

What I have tried:

I have googled the Windows Installer directory structure but could not find any thing meaningful.