I've seen a couple of issues with Worklight 6.2 studio around logging.
To repro #1
<logging consoleLogLevel="INFO" copySystemStreams="false" maxFileSize="400"/>
<logging consoleLogLevel="AUDIT" copySystemStreams="false"/>
Since this line comes later in the file, it takes precedence over the first line for the server. For the GUI, it displays the contents of the first line.
For #2, it straight up looks like if you change the maxFileSize option on the logging line, the server just doesn't pay attention to it, and still wraps at the default (20, I believe). I've made sure there aren't 2 logging lines in the server.xml, restarted the server, etc.
If there is any additional info I can provide to help track these down, please let me know.
This appears to be a known defect.
If you are an IBM customer or business partner and require a fix for this issue, you can open a PMR support ticket and request a Worklight 6.2 iFix to be produced and delivered to you.