It could only be understood that way if there were indeed separate groups of torpedo tubes. If that's the case, then it's ambiguous however you say it -- at least if both the groups and the individual tubes are called DuS and numbered. I wouldn't expect that sort of system to survive as a viable usage, and I would expect the tube groups to be called ghommey or DaHmey and the individual tubes to be called DuSmey.

-- ghunchu'wI'