Dan takes that as a compliment. He assumes that Nikola would only poke at something that was worth while. After a few hours he realizes how long they've been in his lab and points that out to Nikola. "Are you sure you don't want anything to drink or eat?" he asks. He knows there are some weird stories about Tesla's eating habits though, so he assumes that part will be turned down. Still, if there was something that Nikola wanted, Dan wanted to provide it.