These types of questions also come up in the form of asking “if a stock plots above the Security Market Line, is it _____”? The answer to this is undervalued.
Using the example above, if the expected return is 9% and CAPM requires 10%, it means that for the level of risk (beta) you are taking on, you should be earning 10%, so 9% is not a good deal for that level of risk. If the E(R) were 15%, you’re earning more expected return than you should at that level of risk.