This user has accepted no answers, answered no questions, received no bounties, and received no association bonus. They also seem (as far as I can tell) to have only edited their own questions. If any questions/answers were deleted, the rep would be removed, so that doesn't affect anything either. The only activity of this user is the asking of two questions - this and this. The former question has a score of +1/-4 and the latter a score of +0/-1. This means $(1*5) - (4*-2) - (1*-2)$ or $-5$, so in other words, since SE doesn't show negative scores, the user should have a reputation of 1. However, the user has a reputation of 4.
How did this happen?