A gambler spends $1,000 on his first day playing slots. The second day, he gambles again on slots with the same $1,000 bankroll and wins $800. His balance is now $1,800, a loss of $200 from the first day.

So, the image you provided is completely correct in showing that slot games are indeed luck based games. But the title you gave is completely wrong. Gambling is not designed to beat the gamblers, but rather the chances of winning are lower, and when you do win, the amount won does not equal all the losses that have been spent.

So that's why I always stick to a small budget when playing slot. Because when I'm lucky, the amount I win won't equal the amount I spent.