The amount (in percentage points) by which a security has outperformed or underperformed the S&P 500 for the given time period. It is calculated by subtracting the S&P's total return over each period from the total return of the security for that period.
For example, if an 8% appears in the +/- S&P 500 column for the one-year period, it means the security has outperformed the S&P by eight percentage points for that period.