We are told that there are $63 million of shares in issue that have a par value of $0.25 each. The 63*4 is calculating the number of shares in issues, but it maybe easier being written as 63/0.25.
The 4/3 is the bonus fraction that is applied to the shares in issue before the bonus issue took place. So here the 4 is the number of shares after the issue and 3 is the number of shares before the issue.