Total outstanding number of shares is impacted immediately. But given the 6 month hold period, they will not enter the 'float' of shares available for trade until that period is over and only then if the individual sells. I would assume that - like me - most PP participants are not looking to sell their shares after a short period of time, but are instead amassing a large position in what we hope turns into a valuable company. In that sense, you're unlikely to see a lot of these shares hit the market.