[yocto] Crownbay .hddimg partition is corrupt...but works?

[r10kindsofpeople]

I've been following with interest the thread on creating multiple
partitions, but before I get there, I seem to have a stumbling block.

I've been using dd to copy the .hddimg onto an SDCard and booting from
there.  It works fine.  The core-image-minimal image is about 32MB,
copied onto a 16GB card.  When 'boot' is mounted under Ubuntu 12.04, I
see the 5 files totaling about 31 MB with about 1 MB free.

But when I run 'parted' on /dev/mmcblk0, I see one 16GB partition
using the fat16 file system.  'parted check' warns me that Partition 1
is 16.0GB, but the file system is 32.2MB.  GParted basically throws up
its hands in frustration and gives up.

It seems to me that before I start trying to get a class created that
will create the partitions automatically, I ought to first figure out
how to create the partitions by hand, but I'm not convinced that the
.hddimg is giving me a solid foundation to start with.

Can anyone give me clues to the why/wherefore of the partition that
the build system is creating?  If I create my own partitions on the
card first, won't the 'dd' operation simply wipe that out and replace
it with the current situation?

I'm using the Crownbay emgd layer, Denzil 7.0.1.

John