Hello Dennis,
please edit the file <service-manager>\config\servicewatcher-sw.yml. Right at the top you'll the section "logging" where you can add the following two lines with your desired values:
maxDays: 10
totalSizeCap: 3GB
It should look like this (for example):
logging:
file: ./../../logs/services.log
config: ./config/logback.xml
maxDays: 10
totalSizeCap: 3GB
Best regards
Nicolai