I think you are misunderstanding the summary.
It's saying that Win 7 Pro is the default OS and that the drive containing the boot files is D (W8.1)
It's normal (and mandatory) that W7 boots Via W8 since there is no forward compatibility of the bootmgr module.
(i.e. Vista cannot boot W7 or W8, W7 cannot boot W8).
If you boot W7 and run Disk Management you should see that W7 is "boot" but W8.1 is "system" and "active".
That seems to contradict the above, but DM nomenclature is quirky in its use of English compared to the rest of the computing world.
Disk Management flags have the following meanings
"boot" = "this is the system you're running"
"system" = "this is where I found the boot files for the currently running system"
"active" (on the first HDD in the BIOS boot sequence) = "this is where I started the search for the boot files"
"active" (on subsequent HDDs in the BIOS boot sequence) ="this is where I will look if I don't find something in the MBR on the first HDD"