Imagine that Rafael hit the baseball with a force of 25 N and what came out was a 5 N force.
The bat did not give Rafael an advantage, because the force that came out was less than that applied.
Mechanical Advantage in this case = Force output / Force applied
= 5 / 25 = 1/5 = 0.2
Mechanical advantage = 0.2. This is actually a mechanical disadvantage.
Because the value is less than 1, if it were greater than 1, then it would really be an advantage.