Unfortunately it seems that those how go delving deep into logs and folder size, etc. often haven't the knowledge to understand what it is telling them.
I have restricted my log sizes, etc. but for me that doesn't make a great difference and I tend to keep my nose out of the logs and folders, unless I have a problem that I'm investigating.
Normally that is when I look for reference purposes (like this topic), other than that I let avast take care of itself.
Saving a whole 69MB is a bit of a joke in these days of monster hard disks. If your system is really that short on space that 69MB makes a difference you need to get a bigger drive or take a serious look at what you have installed, is it absolutely essential.
Hopefully he won't take a look in the defs folder as that fluctuates by 66MB a pop as a new defs folder is created and the old one subsequently removed during avast housekeeping..