"1 indicating a coupon and all other outcomes indicating no coupon"
Probability is (number of successful outcomes) / (number of possible outcomes)
Theoretical Probability of rolling a 1: 1/8
Experimental Probability of using coupons: 4/48 = 1/12
So, the experimental probability of a customer using a coupon (that is, 1/12) is smaller than the theoretical probability of rolling a 1 (that is, 1/8).