It's a positive number. Here's why:
Let's say he earned $10 and only spent $9. This means he would have $1 left. That isn't much, but it is still a positive number because he did not spend more than he made. For example, if he spent more than he made, it would look like this: He made $10, but spent $11, which leaves him with a debt of $1, which can be represented by $-1.
