Your company's valuation immediately before new investor money lands in the round.
Sequoia led Snowflake's Series F at a $1.5B pre-money on a $450M check, putting post-money at roughly $1.95B. Two years later, Snowflake's September 2020 IPO priced at $33B, the largest software IPO ever at the time. The pre-money is the number that determined how much of that upside Sequoia owned.