Alas our group already made a ruling the other way, so that is what we will use for this game.
Our logic went something like this: It takes 10 Q to transport 1 PTU. 1 PTU equals about 15,000 people. A cutter can transport 0.25 Q as passengers so that would be about 3,750 people. I have heard it mentioned that colonists are probably transported in cold-sleep so they take up 1/10 the space. If we assume they are awake and not sleeping then we still have a passenger capacity of 375 people in a single cutter. I figure the crew of a cutter is, at most, 5 people. So if the crew alone is in the cutter they are using 1/75 the normal life support. That ought to give them an endurance of 4 x 75 = 300 days but instead the rules say 12 days if it is crew only.
With all that in mind the group decided that even if they are carrying cargo, the crew alone ought to get the 12 days listed under Crew Only.