Each and every day you play the game, you can log in and receive a mysterious reward - it might be Materials, XP points, Guano, or even Pot bucks! If you make sure to log in and collect your reward every day, your reward counter will move up and on the 7th day, you get a WHOPPING 15 Pot bucks!!!
And that's not even the best part: on the 8th day, you start all over and can collect your week of rewards again!!!
If you miss a day, your reward counter will start from the beginning again. Don't worry though -- you'll always be able to start over and you'll always get a reward!! :D