You get four tries, most of the time you'll use three of them and if in three tries you haven't made a ten yard advance to win a new set of downs you'll use that fourth go to give the ball to the other team as far away from the goal you defend as your kicker can accurately punt it. There are times though when you will use that fourth try, the saying "go for it on fourth" meaning do or die on one last try… when you only need inches, when the time clock says now or never, when pride and desperation say it's time for the boys of today to stand forth and aspire to the august company of yesteryear's hero revered for enforcing a noble defense of the greater glory of and blah blah blah. That sort of thing. What we American's call "Football" that I've heard the world calls "Grid Iron." Rules of the game, a bit of flavor and tactics from the game.
So you see, a second (down) and seven (yards to go) is about as common a situation as you're likely to run into. When the focus is a work such as this rather than mock combat posturing as athletics a second and seven translates to mean "Ok, theory holds and it works on paper… so what do you have by way of evidence for any of this? Anything? Or is this just hot air sans balloon?"
I'm not complaining, that's pretty much how it has to be even though for those who dare put forward an idea those seven yards can elongate into a lifetime of uncertainty. It's the price you pay to step out on the field of thinkers in the first place.
