Resources entrepreneur Tolga Kumova admitted to the Federal Court it was a mistake to boast on Twitter that a metals mining tenement he had a financial interest in was worth $5.3 billion, when in fact it was worth $532 million.

In an ongoing defamation battle, Mr Kumova said on Thursday the $4.8 billion difference was a mathematical error related to a September 2017 tweet, which claimed New Century Resources sat on a $US12 billion zinc, lead and silver deposit, shortly after the metals explorer listed on the ASX in July 2017.