as he said, it's that "may" that calls it.
it's sort of a quick stop over kinda thing. as you're buzzing along, you find a freighter that's going (roughly) the same direction, so you dock up and do some quick trading, then go on about your business. it's one of those helpful cards.
Especially helpful right after being pirated to steal your cargo that could "win" the game for you in your next turn... (from experience as the pirate)