It seems to me to be more than the definitions. I've got 128 MB in the Setup folder. Why is it so big?
Another thing, when I updated to 1466 from the interface, Programs and Features told me Avast was 350 MB, but I uninstalled and did a clean install and only had 238 MB. So some of the large disk usage may not be totally accurate. Or maybe updating from the interface is simply causing bloat, I don't know. My laptop with Vista normally reads disk usage accurately, so I tend to think the latter.