it doesn't even say how many tickets total there are or how they draw the numbers
I think it works like this:
4 people decide to join the raffle.
person 1 takes 5 tickes
person 2 takes 10 tickets
person 3 takes 20 tickets
person 4 takes 1 ticket.
So total there are 36 tickets
Person 1 has 5 out of 36 chance to win so: 13.8%
Person 2 has 10 out of 36 chance to win so: 27.8.%
Person 3 has 20 out of 36 chance to win so: 55.6%
Person 4 has 1 out of 36 chance to win so: 2,7%
The more tickets you buy the higher the chance that you win.
This is how I think it works.