This depends on how the liquidation preference is structured. Sometimes each new Series is made more senior than the prior series, so the last money in gets paid first - in that case if the last investor put in $100m they would get it all out before any of the other investors got paid. In other cases, the different series of preferred stock have a "pari passu" preference, meaning they all have equal priority - so in that case, you'd calculate each investor's liquidation preference as a percentage of the total liquidation preference owed to all investors, and they'd split the available proceeds according to that percentage.