When you receive a coupon in your inbox, you can redeem it.
The redeem steps are as follows.
1.   Enter the game lobby, click and enter your inbox.
2. Click the Redeem button in the coupon message (In this case: Take this Kitty Coupon!).
3. The pop-upwindow will appear, then you can click the green button to enter the purchase page (In this case: ONLY $60 bottom). The price you see in this page is the finalprice. 
*When you receive a coupon in your inbox, you can redeem it. Please be notified that these coupons are dispatched randomly, irregularly and with time limitation. The discount rate and final price are different between players. If you would like to redeem the coupons, please make sure to click your inbox within the time limitation.