Apache 1.3 log file size specification

I was told that the logs on my web server rotates when they reach a
size limit of 500M - actually 512M I think, but when I look into
*.conf files including logrotate.conf, I don't see any size
specifications of 500 / 512. I see 1M, 2M, and 4M though.

Is there another place where this can be specified.

Thank you in advance ...