I'm filing my Schedule K-1 with TurboTax and got this checkbox to check - "All of my investment in this activity is at risk". What does this actually mean?

Here's my situation:
* worked for an LLC last year that didn't generate any revenue
* I've "invested" my time (duh), car (went to business meetings), and my laptop.
* When I was hired, I got an equity stake in this LLC

Long story short, if I check that box, my federal refund goes up by a few hundred bucks. But can I good conscience check that box? What if I get audited, how can I prove that my "investment" was at risk? I haven't invested any cash.

Thanks,
J

PS: I'm in CA if that matters