Clarify rules

Initially I read it to mean I only get extra cells while I have <12 cells *on board*.
That would make little sense (you can't do anything until you're wiped out) but I was perplexed why I'm still getting cells to place and it took me a code walk to understand it's <12 cells *to place*...
Hope now it's un-ambiguous.

P.S. Thanks, it's fun!