The downvotes happened before the upvotes, so he didn't lose any reputation from it (you can't have negative reputation).
Reputation is floored at 1. So a new user will gain net positive reputation if downvotes are followed by upvotes even if, in normal circumstances, it would have the net effect of decreasing reputation.
Personally I think the floor is flawed: it can artificially inflate new-user reputation due to sympathetic upvoting.
Look at, for example, what you can do with 15 rep: https://meta.stackoverflow.com/help/privileges