I was a poll inspector for 10 years in my California city. Once the polls close at 8 pm, we began tearing down and packing up the polling station, taking the casted ballots out of the ballot box and counting how many ballots were used, packing and sealing the ballots in a box, doing the end-of-day paperwork, and delivering the ballots and supplies to the central pickup point by around 9 pm.
Once all the polling stations for a given location have been picked up, everything is taken to the Registrar of Voters office for tabulation. The in-person ballots are run through the voting tabulation machines and the Mailed-in ballots and the Mail-in ballots dropped off at the polling sites are processed by a machine that scans the envelope and signature comparing it to the voter's signature stored in a computer. It the ballot passed it's sent to be opened, tallied, and filed with the other voted ballots.
Much of the work sounds like it's automated but a lot of it is still done by hand and that takes time. Unless the bill provides funding to County Registrar of Voters to hire more people to work, I don't see how they'll count them all in 13 days. I hope they can do it but right now, I'm skeptical.