A quarter is another way of saying one fourth, in this setting, one fourth of a year = three months. Quarterly means something that happens every 3 months. Edit
Outfielder Ty Cobb, whose career ended in 1928, has the highest batting average in Major League Baseball (MLB) history. He batted .366 over 24 seasons, mostly with the Detroit Tigers. In addition, he won a record 11 batting titles for leading the American League in BA over the course of an entire season.
His most significant record is his batting average of 99.94. One of cricket's most famous statistics, it stands almost 40 runs higher than any other batsman's average. Don Bradman is the only player in the world to have scored 5000 runs against a single opposition: 5028 runs against England.