It is a bit silly, but try thinking of it as "one developer who helps makes ten others be twice as productive". It could even be a non-technical manager who is

It is a bit silly, but try thinking of it as "one developer who helps makes ten others be twice as productive". It could even be a non-technical manager who is really good at taking care of all of the non-development work for the team, allowing them to focus on what they do best.