How did Charley ‘reach’ the third level of the Grand Central Station?

One day, Charley got late from his office. He wanted to reach home soon. Therefore, he went to the Grand Central to catch a train. He walked down to the first level, and then walked down another flight of stairs. He thought he had reached the second level again, but he got lost. He walked down a corridor. He thought it was wrong, but he walked on downward. He walked down a short flight of stairs. He thought that he had reached the second level again. However, actually he had reached the third level.