How many outs?

[SlyR]

I'm having difficulty with a passage in Gary Carson's book.
He states that if you hold J [img]/images/graemlins/spade.gif[/img]J [img]/images/graemlins/diamond.gif[/img] and the flop is 9 [img]/images/graemlins/heart.gif[/img]7 [img]/images/graemlins/heart.gif[/img]3 [img]/images/graemlins/club.gif[/img], and your sole opponent holds either J [img]/images/graemlins/heart.gif[/img]9 [img]/images/graemlins/diamond.gif[/img] or J [img]/images/graemlins/club.gif[/img]7 [img]/images/graemlins/club.gif[/img], then your opponent has between two and four effective outs.
I have no idea how he arrives at this number of outs. I figure the case Jack has him drawing dead, as does pairing any other card on the board. So he only has two outs, right?

Then, he goes on to explain that with A [img]/images/graemlins/club.gif[/img]7 [img]/images/graemlins/club.gif[/img] he effectively has seven outs. Huh? I count five. Where are these extra two coming from?

[CheckFold]

back door flush draws.

[SlyR]

How does one arrive at 2 outs for a backdoor flush draw?

[CheckFold]

There's about a 20 to 1 shot of making a runner runner flush.