Warren Buffett had a good day.

IBM shares surged 8.9 percent Wednesday after the company reported better-than-expected third-quarter earnings the previous evening.

The Oracle of Omaha's Berkshire Hathaway owns 54.1 million shares of IBM as of June quarter-end, according to FactSet. With Wednesday's more than 14 point rally in the shares, Buffett's company is up approximately $775 million on its position, assuming it hasn't sold shares since then.

Ironically Buffett told CNBC's Becky Quick in May that he was wrong on his initial appraisal of IBM as an investment.

"I was wrong … IBM is a big strong company, but they've got big strong competitors too," Buffett told CNBC. "I don't value IBM the same way that I did six years ago when I started buying ... I've revalued it somewhat downward."

SEC filings revealed Buffett's company sold 10.5 million shares of IBM in the June quarter, according to FactSet.

IBM shares are down 3.9 percent year to date through Wednesday's close versus the S&P 500's 14.4 percent return.

This was the biggest jump in the stock since Buffett has owned it. IBM last moved this high in one day in January 2009.