When Xiao Ming calculated 2.5*(□+4), he miscalculated into 2.5*□+4 because of his carelessness. How much is the difference between his calculation result and the correct value?
小明在计算2.5*(□+4)时，因粗心错算成2.5*□+4了，他的计算结果与正确值相差多少
<gadget id="calculator">10 - 4</gadget>
<output>6</output>

<result>6</result>