The chance to win the $15,000 Rolex is even lower.
Every time you spin the wheel of fortune, a random 8 digit hexadecimal number is calculated and is converted to a decimal number. That's divided by 4.294967295 and then rounded down to the nearest whole number.

The only 8 digit hxadecimal number that can give you 1 billion is FFFFFFFF. This means that the chance of winning the $15,000 Rolex is 1 in 4,294,967,295.