Free with a tank full

A gas station owner in Alabama was trying to increase his sales.
So he put up a sign that read,
"Free Sex with Fill-Up."
Soon a local redneck pulled in, filled his tank and asked for his free sex.
The owner told him to pick a number from 1 to 10.
If he guessed correctly he would get his free sex.
The redneck guessed 8, and the proprietor said,
"You were close. The number was 7.
Sorry. No sex this time."
A week later, the same redneck,
along with his brother, Bubba,
pulled in for another fill-up.
Again he asked for his free sex.
The proprietor again gave him the same story,
and asked him to guess the correct number.
The redneck guessed 2 this time.
The proprietor said,
"Sorry, it was 3.
You were close, but no free sex this time."
As they were driving away, the redneck said to his brother,
"I think that game is rigged, and he doesn't really give away free sex."
Bubba replied, "No it ain't, Billy Ray.
  It ain't rigged.    My wife won twice last week."