Whose record did Nolan Ryan break when he struck out the 3,509th batter of his career?

On April 27, 1983, Ryan struck out the Montreal Expos Brad Mills for the 3,509th K of his career to move past Walter Johnson into sole possession of first place on the strikeout list. However, later that season, Steve Carlton challenged Ryan and eventually passed him on June 7, 1983, when he recorded his 3,526th strikeout — one more than Ryan. The two went back and forth for the rest of the season, but Ryan eventually passed Carlton for good during the 1984 season.