The alarm clock at Grandma Zhang’s house is 4 minutes faster per hour (the accurate hour and minute hands should move one circle per hour, but the minute hand of this clock moves more than 4 divisions per hour). At 21:00 last night, she set the alarm clock to Beijing time. Aligned, and at the same time dialed the clock to the alarm at 6:00 this morning, Grandma Zhang heard the alarm ringing how many hours earlier than Beijing time at 6:00 this morning. (Score expressed in fractions)
张奶奶家的闹钟每小时快4分钟，(准确的钟分针每小时应走一圈，而这个钟的分针每小时走一圈多4格)，昨晚21：00，她把闹钟与北京时间对准了，同时把钟拨到今天早晨6：00闹铃，张奶奶听到闹铃声响进比北京时间今天早晨6：00提前了多少小时．(得数用分数表示)
<gadget id="calculator">60 / 64</gadget>
<output>15/16 = around 0.9375</output>

<gadget id="calculator">9 * (15/16)</gadget>
<output>135/16 = around 8.4375</output>

<gadget id="calculator">9 - (135/16)</gadget>
<output>9/16 = around 0.5625</output>

<result>9/16 = around 0.5625</result>