Grandpa Li participated in the rural cooperative medical insurance, and the terms stipulated that the insured's hospitalization medical expenses compensation set a deductible line, and township-level medical institutions paid 100 yuan, and 70% of the part above the deductible line was compensated. That is, compensation fee = (medical expenses - deductible line) * compensation rate. In January this year, Grandpa Li was accidentally injured and fractured. He was hospitalized in Jingdian Hospital for 28 days. The medical expenses totaled 3,100 yuan. According to the terms and conditions, how much does Grandpa Li only need to pay by himself?
李爷爷参加了农村合作医疗保险，条款规定：参保者住院医疗费补偿设起付线，乡镇级医疗机构为100元，在起付线以上的部分按70%给予补偿．即补偿费=(医疗费-起付线)*补偿率．今年一月份李爷爷意外受伤骨折，在镇定点医院住院28天，医疗费用共计3100元，按条款规定，李爷爷只需自己付多少元？
<gadget id="calculator">3_100 - 100</gadget>
<output>3_000</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">3_000 * (3/10)</gadget>
<output>900</output>

<gadget id="calculator">900 + 100</gadget>
<output>1_000</output>

<result>1_000</result>