The FAQ says that your calculation of the Sharpe ratio uses "the time series of the daily relative returns during a Competition".
The 1966 formulation of the Sharpe ratio uses the difference of returns and a risk-free return (such as government security), while others might use a benchmark against the relevant security (S&P500).

How are relative returns calculated for the Sharpe ratio in Competition scoring?

The FAQ says that your calculation of the Sharpe ratio uses "the time series of the daily relative returns during a Competition".
The 1966 formulation of the Sharpe ratio uses the difference of returns and a risk-free return (such as government security), while others might use a benchmark against the relevant security (S&P500).

How are relative returns calculated for the Sharpe ratio in Competition scoring?