I can understand an email like this can freak you out.
But I think there is nothing to worry about.
My theory is that you recently updated the iTSec plugin which triggered a ‘first run’ File Change Detection scan. This due to the fact that in the latest iTSec plugin release (7.0.x) the File Change Detection scan engine code has totally been rewritten.
The feature should upgrade keeping old data but it looks like that didn’t happen.
So after upgrading the plugin you got a typical ‘first run’ File Change Detection result.
Whenever a File Change Detection scan runs for the first time in an env it will report a large amount of Added files (0 Removed, 0 Changed).
A File Change Detection scan will normally compare a (in the database) stored file list with what it just scanned. The first time there is no stored file list. So it has nothing to compare with. So all scanned files are reported as Added.
Just keep an eye on it. If the feature continues to report 12416 Added, 0 Removed, 0 Changed files then it may be malfunctioning. Which could be another reason why this is happening.