A night-shift station, a cupboard that’s been disturbed, and someone who shouldn't be there—that kind of tight setting is great for slowly building suspicion. Are the clues for the three-digit code hidden in what the characters say? Really curious how the dialogue connects to that first puzzle.
Thanks for the question! For that first lock, the answer comes from what you read around the station rather than from conversation: the paperwork and signs matter more than the train times. The later puzzles in the full game lean much more on what the people at the station tell you. If you get stuck, the in-game hints help step by step, with no penalty.