The more card packs you open over time, the more likely you are to be awarded the same cards more than once. You can exchange these cards for amazing prizes!
Each duplicate card you get fills the 'Star' bar at the bottom of your screen (within the 'Get Gift' tab, in the Album's upper menu), based on its number of stars. Once the bar is full, you can play and win a prize!
You can redeem another gift every 12 hours (given that the ‘Star’ bar is full), so make sure to come back and collect them all!
Please also note, that you can upgrade your gifts, by filling the 'Gift Level' bar, simply by opening more and more gifts.
Good luck and have fun!