What makes you think you're doing something wrong?
According to the output, the USB camera was mounted at /dog. You should be able to read and write to the camera by accessing any file under /dog.
The message also says, you need to run two commands before you unmount the camera:
syns and
sync
Once those two commands finish, then you can unmount the camera by issuing
umount /dog. The commands are there to guarantee that any information you write to the camera gets flushed out of the system before you unplug the USB connection.
