How to use coupons?
There are four value for coupons: 5cny, 10cny,20cny 50cny
The effective period of coupons are 30days (from the day you converted that coupon with your integration)
when you submit your order you can use coupons to deduct the service fee, but each order just can use one coupon. The difference will not return when your service fee is less than the value of that coupon.