Facebook Inc (FB) CEO Mark Zuckerberg disclosed new information about his 2014 deal to buy the VR company Oculus during his public appearance in court on Tuesday. The CEO was in a Dallas courtroom to testify in the ongoing lawsuit by video game publisher Zenimax against Oculus. Zenimax claims that the Oculus Rift VR headset is partially based on its stolen technology.

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Facebook (FB) paid an additional $1 billion for Oculus

According to The New York Times, Zuckerberg disclosed during his testimony that the social media giant paid an extra $1 billion for Oculus in employee goal targets and retention packages. When the Oculus deal was announced in 2014, the social media giant said that it paid $2 billion.

Zuckerberg also spoke about the future of virtual reality and said he does not think that good VR is fully there yet. He added that it is going to take about five to 10 years of development before they get to where they all want to go.

Oculus CTO John Carmack is at the center of the Zenimax lawsuit. Previously, Carmack ran a video game company within Zenimax called id Software. The video game company is best known as the mastermind behind video games like Quake and Doom.

According to Zenimax, Oculus executives knowingly stole its software and trade secrets through the hiring of Carmack and five of his employees from id Software. Zenimax claims that Carmack violated his employee code by sharing confidential information that Oculus used as the basis for its virtual reality software.

FB founder denies that Oculus’ tech is stolen

Facebook Inc (FB)’s CEO said he had never testified in a courtroom before and denied the accusations that Oculus had taken tech it did not own. Zuckerberg said they are very confident that the products are built on Oculus’ technology, and even the idea that they are based on the technology of some other company is just wrong.

During the testimony, Zenimax lawyer Tony Sammi asked Zuckerberg how fast the deal to acquire Oculus was put together. He replied that Facebook Inc (FB)’s legal due diligence into Oculus’ business was done in just one weekend.

According to Gizmodo, Sammi had asked in court, “Your plan was to begin legal diligence on Friday, and sign the deal on Monday?”

The CEO replied, “Yep.”

If the tech giant loses the lawsuit, it could pay as much as $2 billion in damages. Oculus co-founders Brendan Iribe and Palmer Luckey are scheduled to testify this week.