Negative numbers are probably convenient, if your background is in a field, where numerical calculations are the norm. Traditional accounting is better justified from a mathematical perspective, as mathematics is more about definitions than calculations.

There are usually multiple levels of abstraction in code. When choosing the one to use for a particular task, it's a good idea to prioritize both simplicity and conceptual clarity. Bad things often happen, when the two priorities disagree. And you should try to use the same terminology and same concepts as the user as much as reasonably possible. Otherwise it's easy to make wrong choices by thinking about the problem from a wrong perspective.