I'm getting "Autoptimize cache size warning" emails. Looking at the code, I can see that the plugin is comparing the size to 536870912, which is 512MB, but the actual size is 266506240, which is only 254.16MB. Below is a capture from cPanel's Disk Usage page:

The autoptimize_stats transient is currently unset, so the plugin seems to be counting file sizes incorrectly.

There is no overriding code for any of the filters used by the plugin in my child theme or in the parent theme (Divi, if this makes any difference).