Actually the log have a log rotation for almost each probe to stay with 2 files only.
So it will retain the current log + _log ( 2 files in general)
File log size is set via probe.cfg, so you can set to generate a file with 100 (100kb) or 10000 (10MB), etc.
Finally the file details is based on loglevel size like 0 or 5 ( 0 will show just few info) and 5 for Debug info
Actually the recommendation is to leave the logs all set to 1, and if have any trouble/issues that need a troubleshoot for our side, we ask to increase the loglevel and logsize.
Just spectrumgtw or other specific probe may have more files and we set the size and how many log files will be generated in the log4j file.