The question was "What is the potential difference between the electron’s initial and final points?" And you've hit the nail on the head, the electric potential difference is 0.3V, but it is not one of the multiple-choice answers. And you've noticed that the electric potential energy difference is the same as one of the possible answers (answer c).
This is a very important skill for exams - trying to interpret the question, even when the question is worded badly. I think this is one of those situations, where the question wants the electric potential energy difference, but they only wrote 'potential difference'.