At the start of a fitness challenge, $80\%$ of participants reported their primary goal was "Weight Loss", and $20\%$ reported "Muscle Gain." At the end of the challenge, $30\%$ reported "Weight Loss" as their primary goal, and $70\%$ reported "Muscle Gain." Altogether, $x\%$ of the participants changed their primary goal during the challenge. What is the difference between the maximum and the minimum possible values of $x$?