The factory produces a batch of watches. It plans to produce 300 watches per day, and it is completed in 5 days. After two days, 600 watches have been produced. How many watches are left?
工厂生产一批手表，计划每天生产300只，5天完成，两天后已经生产600只，还剩多少只没有生产？
<gadget id="calculator">300 * 5</gadget>
<output>1_500</output>

<gadget id="calculator">1_500 - 600</gadget>
<output>900</output>

<result>900</result>