Philadelphia will start its recount for the Pennsylvania Republican Senate primary on Sunday.

The recount is scheduled to begin around 1:30 p.m. It will be largely completed within a few hours, city elections chief Lisa Deeley said. By the end of the day, she expects to be done counting all available votes.

That will leave just a small number of votes that can’t be counted until Tuesday. Elections officials voted Friday on whether to count or reject the very last ballots that had yet to be part of the initial count. There’s a two-day appeal period before those can actually be tallied, so they won’t be counted — and then immediately recounted — until Tuesday afternoon.

So while Philly’s recount technically won’t be done until Tuesday, Deeley expects the “vast, vast majority” of votes to be run through Sunday.

Celebrity doctor Mehmet Oz is leading former hedge fund CEO David McCormick by less than 1,000 votes in the nationally watched primary. The winner will face the Democratic nominee, Lt. Gov. John Fetterman, in a critical general election that will help decide which party controls the Senate.

» READ MORE: The Pa. Republican Senate primary is heading to a recount with Oz narrowly ahead of McCormick. Here’s what to expect.

Pennsylvania’s acting Secretary of State Leigh M. Chapman, in ordering the recount this week, said counties could begin as early as Friday, and must begin by next Wednesday. Many counties had been preparing to start Tuesday or Wednesday. That means Philadelphia’s recount will also be one of the first to be completed.

During the recount, ballots must be read on different equipment from what was used the first time. Philadelphia’s mail and provisional ballots will be run through different models of high-speed scanners. In-person votes were cast on voting machines that scanned the votes individually throughout election day, and will be run through high-speed central scanners during the recount.

The official reading of the results of the first count and recount will be held Tuesday evening.

Workers will review any ballots with over- or under-votes, meaning too many or too few candidates were selected, or stray marks. A “voter intent” standard is used, meaning elections officials use their best judgment in trying to interpret which candidate a voter meant to support.