Each interviewer scores you - in four categories: Algorithms, Coding, Communication, Problem-Solving.
A means: clean working code, no syntax errors, excellent communication, asked clarifying questions, had time for follow-ups.
A means: working code with minor issues, less time for discussion.
A or below: struggled significantly, poor organization, major errors.
Scores are not averaged. One among three s is likely a rejection, not a average.