If you simply calculate it this way, it is 6000*0.05%*30=90 yuan. However, interest is actually calculated based on the actual number of days of use. If there is a monthly billing date, compound interest will be charged after the billing date. Compound interest means that the interest paid before is added to the principal to generate interest again. For example, when 6,000 yuan reaches 20 days, the interest generated is 60 yuan, and this day is the billing day. Then starting from the day after the billing date, the daily interest will be 6060*0.05%=3.03 yuan.