If you change some parameters in
/etc/logrotate.d/* the most common way to use the new configuration is to call logrotate like:
That way will read the whole configuration of logrotate using parameters like minsize, age and so on.
But you can force logrotate to ignore those parameters so the rotation will happen even if the size is smaller than minsize (minsize as an example)
Simply call logrotate as seen from above with the
logrotate -f /etc/logrotate.conf