The XYZ online bookstore in Jakarta, Indonesia wanted to improve their marketing strategy to increase book sales. They used a method called RFM analysis with the K-means algorithm to group customers based on their buying behavior. By analyzing customer data, they found three types of customers: loyal, new, and lost customers. They also identified two types of customers based on their value: best customers and uncertain customers. This approach helped the bookstore understand their customers better and tailor their marketing efforts accordingly.