A stable or improving unemployment rate is generally seen as a positive indicator for the economy, which can lead to increased consumer spending and business investment. This can have a positive effect on the stock market, and as SPY is an ETF that tracks the S&P 500, it is likely to be impacted by overall market sentiment. Since the rate came in below estimates, this could be interpreted as a stronger-than-expected labor market, which might lead to a short-term positive impact on SPY.