The actual output is 20% less than the planned output, that is, the actual output is the planned output
实际产量比计划产量少20%，就是实际产量是计划产量的多少
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<result>4/5 = around 0.8</result>