DD bs=4M option on USB mem-stick creates false format

[kAt <giathnygeia@openmailbox.org>]

dd if=/media/------/image.iso of=/dev/sdb bs=4M; sync

the image works but the format of the drive seems false
gparted when starting says that linux thinks it is a 256k block and not
the 4m it indicates.  It shows on an 8G drive an empty space of 28G

Is it the option of bs=4M that creates this problem. The free space can
not be formatted and partitioned.  As Gparted tried to claim and format
this space as a 6.7G which seemed right it crashed.

Any advise would greatly be appreciated
kAt-rin