Per the DX SaaS Guide:
Update the Log File History and Size
Open ./config/application.yml and then add the following hidden properties:
By default, the log files rotate when they reach 10 MB. The rotated log files are retained for seven days, unless you update the value of this setting.
In this example, the log files are retained for 14 days.
Define the size of the total log archive. When the archive size exceeds the threshold, backups are deleted. The supported units are: byte; kilobyte; megabyte; gigabyte; terabyte