Empathetic to her plight, Spock said, "I hope it gets better for you." There seemed to be things that Uhura didn't want him to know, and so he didn't push for too many specific details. He figured that Uhura would share things with him when she was ready. Though he was curious about her job and her transfer and why she seemed so unhappy about her current situation, he didn't want to push.
"Is it a very dangerous job?" He asked, brow raised. Spock didn't want to picture Uhura in a truly dangerous job. No one really wanted that of someone they cared about.