If I understand the rules jack’s operating under correctly, and I probably don’t, someone from his current time period (late ’90s) would have to tell him that computers were the future as an absolute statement (not turned into a question by the addition of that “no?” at the end) for him to be able to acknowledged the truth of it in any way. Even then, the fact that he knows it as a fact, not simply as a belief, in a way impossible for people of that period, would probably keep him from being able to state it with certainty.