You are not accounting for liquidation preference correctly. When someone gets a 1x liquidation preference first they get their money back, then they get an equal portion to what is left. So in the case of the 3rd round, first they got their $40M back, but they retained 8% of the pool. Same with the 7M etc. Call it $50M off the billion right off the bat, leaving 950 million. Doesn't really dent the number (reduction of 5% for the founders, so they each walk away with $128M, but that is still 7 million less). Also, this assumes no advisors got shares or board members got shares and that really early hires got no shares outside of the ESOP, which is unlikely). I would guess they probably each walked away with $100M after everything was said and done.