Why Alexandria Ocasio-Cortez nominated Bernie Sanders at the DNC, and how many delegates he got

It had to do with the convention's roll call procedures.

"If you were confused, no worries!" Ocasio-Cortez tweeted. "Convention rules require roll call & nominations for every candidate that passes the delegate threshold."

Ocasio-Cortez, along with former president of the United Auto Workers Bob King, gave the nominating speeches for Sanders, while Sen. Chris Coons and Rep. Lisa Blunt Rochester did them on behalf of Biden. The speeches were followed by the roll call, during which delegations from 57 states and territories cast their votes for each candidate based on the results of the presidential primaries.

Sanders ended the roll call with 1,151 delegates to Biden's nomination-clinching 3,558. Biden will formally accept the nomination for the Democratic ticket on Thursday night.

As the DNC wrapped, Ocasio-Cortez voiced her support for Biden on Twitter.

"I deeply look forward to fighting for our future together and reclaiming our democracy in November," she tweeted, before going on to thank the DNC for having her deliver Sanders' roll call nomination speech.

The progressive lawmaker also took to Instagram Live to further call on her followers to support Biden this November. "The moment Joe Biden is elected, we continue our fight for guaranteed healthcare. We continue our fight for living wages," she said.

ABC News' Ashley Brown and Kendall Karson contributed to this report.