Here's what Facebook's Mark Zuckerberg didn't answer during first Congress hearing

Facebook founder Mark Zuckerberg was forced to give answers to lawmakers, and some of the 2 billion users of his platform, when he was called for a televised reckoning over his company’s data scandal.

Questions over a close to six-hour Senate session ranged from his business model to Russian interference, though the 33-year-old former wunderkind repeatedly deflected some lines of inquiry.

Zuckerberg will testify again to the Energy and Commerce Committee at the House of Representatives, and lawmakers may require a status update to some of the issues he left unanswered.

Cambridge Analytica

The issue that compelled Zuckerberg to wear a suit and go to Washington stemmed from the Cambridge Analytica scandal, where a consultancy that later worked for President Trump harvested up to 87 million user’s Facebook data, many without their consent.

Related: Lawmakers grill Mark Zuckerberg over Trump-connected data scandal

Facebook blamed the breach on the professor who set up an app for Cambridge, who is banned from the service along with the company.

Revelations from whistleblower Christopher Wiley and others have showed that Facebook knew about the alleged violations of its terms in December 2015, though Zuckerberg would not answer a question from California Democrat Sen. Kamala Harris on why his company did not inform users until after the scandal broke this year.

“I don't know if there were any conversations at Facebook overall because I wasn't in a lot of them,” he answered as to whether there was a conversation where Facebook executives decided to keep the issue secret.

Zuckerberg repeated that it was a “mistake” not to tell people, but did not say when the decision was made and he was not sure of what conversations went on around the issue.

Related: Zuckerberg is hypocrite claiming Facebook helped #MeToo movement

Deleting data

The Cambridge Analytica scandal also involved accusations that the company did not delete the Facebook data when told to, and used it as a base for their voter targeting platforms, though Zuckerberg also was unclear about the timeline for users deleting their own data.

He repeated that all data from users can be deleted from Facebook, but did not have answers to repeated questions about how long it takes the data to go away, part of citizens’ digital rights in regulation such as the European Union’s.

Republican Sen. Cory Gardner of Ohio pressed the tech CEO on how long exactly Facebook keeps the data in backups, but was not given an answer.

“I don't know, sitting here, what our current systems are on that. But the intent is to get all the content out of the system as quickly as possible,” Zuckerberg said, adding that he did not know if there had ever been a failure to delete data.

He also said he would have to check with his team to a similar question from Nevada Republican Sen. Dean Heller.

Facebook’s deletion guidelines say “It may take up to 90 days from the beginning of the deletion process to delete all of the things you've posted,” and it was unclear why Zuckerberg did not have clarity on the answer.

Monopoly

One of the hearing’s standout moments was Sen. Lindsey Graham of South Carolina pressing Zuckerberg on his 2 billion users and whether or not he was a monopoly.

“It certainly doesn't feel like that to me,” Zuckerberg said, but failed to give a concrete answer on what other company was a real alternative to his creation.

He said Twitter and Google do provide similar services but kept his answers broad and said that Americans use multiple different apps for social media

Regulation

Zuckerberg also told Graham that he was not opposed to regulation, but provided vague answers on what sort of proposals he would get behind, and often said that Facebook was already changing its own policies.

He said that he supported the Honest Ads Act to bring more transparency to ads — such as those used by Russian trolls in the 2016 election.

But on suggestions of an American law similar to Europe’s General Data Protection Regulation, which he has promised to follow, he said only that the Europeans get some things right and that “everyone in the world deserves good privacy protection.”

Senators also asked Zuckerberg about their own bills, such as Democrat Sen. Ed Markey of Massachusetts proposing a Consent Act putting into law that Facebook must ask users for permission before using their data for other purposes.

Zuckerberg said that he agreed with the principle but said that details mattered, and also said he was “not sure if we need a law” to protect children under 16’s privacy online