Make sure you don't have any exceptional large log files, as it could possibly fail to prune those via PHP. So prune, delete or back them up first.
Global Settings
The global settings are for all log files that are found within the site/assets/logs/ directory. These settings are recognized from the top down and the first setting found will be used. To ignore a setting, leave it blank or enter 0.
Per Log Settings
The per log settings can be used to set a rule for each log separately. These overwrite the global settings for the specified log file.
Archive as ZIP
The zip will be created in the site/assets/logs/archive/ folder. Only 1 zip file per log will be created. Each time the log is added to the zip into a subfolder named Ymd-His and deleted.
Add a config per line. Example: errors:[archive]:[lines]:[days]:[bytes]- Logs currently found: file-compiler, helper, logmaintenance, modules, multisite
errors:1:0:0:0 // would archive the errors.txt log each time the maintenance is run
errors:0:10000:0:0 // would prune the errors log to 10000 lines
errors:0:0:0:1000000 // would prune the errors log to 1000000 bytes