Ships hold 300 goods a piece. Shipping them with less than a full load is inefficient and wasteful. Don't do it unless it's a quick trip.
For example, here are the two loads I have coming from my main colony:
Dasherkins(fldash) 3 Transport 3:34:36
600 Wood, 300 Wine
Dasherkins(fldash) 3 Transport 7:16:08
500 Wood, 200 Wine, 200 Crystal