Problem nuking just a partition?



I'm trying to nuke just one partition of a large drive. I selected the partition ([----] by the drive, [wipe] by the partition) and chose Gutmann. Upon pressing F10, DBAN immediately decided that it was DONE, wrote the report and ended. Upon subsequent bootup with DBAN, the partition was gone. I did this a second time on the same drive with the same results. Finally had to nuke the entire drive and then repartition. That was bearable with that drive but I have another drive (120GB) to do and need to restrict DBAN to the partition that was actually used.

Drive is Western Digital 80GB. Am I doing something wrong?
It was F10. My understanding is that F10 and F12 do exactly the same thing anyway. Even if F12 were to wipe the entire drive, it would not be done instantly. And in that case it would have deleted the second partition at the same time. That did not occur.