It's a different form of guaranteed payout where their value is a multiple on the next round or buyout event.

Both guaranteed payout and multiplier are forms lowering your specific allocation of the evaluation so you get a larger payout vs the rest of that group or future groups.

An opaque method of ensuring investors get a huge payout at the expense of employees with ISOs that convert to common stock. Many startups refuse to share this multiplier with candidates, and will instead insist their equity grant is "competitive with the market" and "very generous."

I wouldn't be surprised if, despite the large-sounding acquisition sum of ~5b, many employees are getting their equity zero'd out and replaced with a back-loaded 4 year grant, with vesting starting today and no credit for time already worked.