The Madrid Maersk is the 2nd largest container ship in the world. In Traveller terms its about 130,000 Dtons (400m long, 58m wide, and about 80m tall with cargo/bridge/below the waterline depth). The crew for this 200,000 gross ton vessel? 28.
Traveller ships have even less crew needs than modern ones, assuming they are jump-capable, since there is absolutely nothing for the crew to manage during jump other than keeping the lights on. Out of jump the crew has to do the same things a ship on the high seas does - manage the watch, navigate to/from their port, and oversee cargo stowage and such.
So having smaller crews is fine. But keep in mind that a smaller crew can do less to respond to an emergency, or do maintenance while the ship is not sitting in a dock. Commercial cargo crews today basically have watchkeeping on the bridge, watchkeeping in the engineering spaces, someone is cooking, and then deckhands do all the scutwork when they aren't docking.
Warships, on the other hand, do a lot more, since they have weapons to maintain, train and practice drills, cook, clean, etc, etc. And they have to be able to depart the ship in small craft for boarding inspections, man weapons to provide cover, maintain small craft, have damage control parties, etc, etc. Warship crews have a lot more tasks and duties than civilian ones.
