"you can forget the interest [suan li k'o chih]." The farmer, who only heard the last four words, misunderstood the doctor as saying, "garlic can cure dysentery," which is pronounced exactly the same.
11. 農夫沒有聽到前面對話，誤把醫生說「算了，利可以止」聽成「蒜痢可以止」。