The article needs clarifying and the quiz at the academy does just that. It's as soon as your br exceeds 10% or
more than double your buy-in.
I'll try to illustrate - Sit with 5% of br. As soon as you reach more than 10% of your br you then proceed to uncheck auto-post blinds. You stay in your seat until you're UTG. If you can't get anything before the BB reaches you then you simply stand up and go once UTG(you've paid for cards up until you're first to act with your SB & BB so you should go ahead and play them). Nobody expects you to fold
hands like AA or KK just because you're up by more than 10%(and for some reason I suspect a few folks will smack you if they find out you did).
Just continue with business as usual until it's time to leave with one caveat. Tighten up a whole lot. Don't take chances with marginal hands, even with some play you'll still be leaving with more than 10%, just try to get your chips in really, really good.
I watched Chris do it and win once at low stakes. I watched him sit with the same plan and lose his buy-in just shy of a double up as well.(this was after the challenge, I guess he was just short stacking for the heck of it)
Again, it's when your stack exceeds 10% of your br. It's not that hard to do. Since every session isn't a winning session, ya gotta capitalize on when you're winning. Leaving when you just double up or don't quite double up because you're being conservative actually hurts you(at least in my own personal experience it does).