The Governor will have 14 days from the 13th to set a date for a special election.
Special elections must be conducted on a Tuesday at least 126 days but no more than 140 days after the issuance of the proclamation.
Gov Newsome will not hold a special election, so the seat will remain vacant until 2021.
I have no doubt the Dems decided against a special election because it would mean one more Republican in Congress and they want to raise money and roll the dice on the bigger turnout for the 2020 general election.