Chang-bo got in trouble on the job because he made a comment. He was complaining about how the factory made so many shoes but his kids never received any.
When Chang-bo got back home after being interrogated his wife yelled at him for being so foolish to make that comment. Also that he was lucky that he got let off so easily if it weren’t for his excellent background.
Chang-bo’s job was to write reports. So when he was told to write one about what’s going on he was trying his best to tell the truth. But when his boss edited it he changed everything and it was all a lie.