The plan is clearly stated under "Six Finger Discount—Community Copies":
New copies are added whenever Six Goblins sells at full price ($12) and/or for every $12 of gross revenue.
Alright! I enjoyed the Critical Misses actual play, but I can't find much on the 6e game you mentioned. I'd be happy to pay full price if it's something my group will actually play, but $12 is a bit too much for me to spend without knowing if it will even make it to the table.
I'll keep an eye out for a community copy and I hope the pouch blesses you with soup this season!