I just wanted to add an update to this now that I'm back at my PC...

This is the data source they used: https://static01.nyt.com/elections-assets/2020/data/api/2020-11-03/race-page/pennsylvania/president.json

And this is what it looks like when you plot it out: https://i.imgur.com/nRekWRo.png

Here is the script (python 3.8+) to calculate the votes and dump the data to an excel spreadsheet so you can play with it yourself.

import pandas as pd
import requests
from dateutil.parser import parse


def main(state):
    url = f'https://static01.nyt.com/elections-assets/2020/data/api/2020-11-03/race-page/{state}/president.json'
    r = requests.get(url)
    api_data = r.json()
    timeseries = api_data['data']['races'][0]['timeseries']
    curated_timeseries = []
    for update in timeseries:
        if (votes := int(update['votes'])) > 0:
            curated_timeseries.append(dict(
                timestamp=update['timestamp'],
                votes=votes,
                biden_share=(bshare := update['vote_shares']['bidenj']),
                trump_share=(tshare := update['vote_shares']['trumpd']),
                biden_votes=(votes * bshare),
                trump_votes=(votes * tshare),
            ))
    curated_timeseries.sort(key=lambda x: parse(x['timestamp']))
    pd.DataFrame(curated_timeseries).to_excel('curated_data.xlsx', index=False)


if __name__ == '__main__':
    main('pennsylvania')