When Xiao Ming calculates a decimal subtraction, he regards the 5 in the hundreds place to be subtracted as 2, and the 8 in the tens place of the subtrahend as 3. How much is the correct answer different from the wrong answer?
小明在计算一道小数减法时，把被减数百位上的5看成了2，把减数十分位上的8看成了3．正确答案与错误答案相差多少？
<gadget id="calculator">500 - 200</gadget>
<output>300</output>

<gadget id="calculator">0.8 - 0.3</gadget>
<output>0.5</output>

<gadget id="calculator">300 - 0.5</gadget>
<output>299.5</output>

<result>299.5</result>